Next Article in Journal
Anaerobic Co-Digestion to Enhance Waste Management Sustainability at Yosemite National Park
Next Article in Special Issue
In Silico Dissection of Regulatory Regions of PHT Genes from Saccharum spp. Hybrid and Sorghum bicolor and Expression Analysis of PHT Promoters under Osmotic Stress Conditions in Tobacco
Previous Article in Journal
Exceeding Probability of Earthquake-Induced Dynamic Displacement of Rail Based on Incremental Dynamic Analysis
Previous Article in Special Issue
Microbial Diversity and Adaptation under Salt-Affected Soils: A Review
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Greenhouse Gas Emissions from Salt-Affected Soils: Mechanistic Understanding of Interplay Factors and Reclamation Approaches

ICAR-Central Soil Salinity Research Institute, Karnal 132001, Haryana, India
Dayal Singh Evening College, University of Delhi, Lodi Road, New Delhi 110003, Delhi, India
ICAR-Central Arid Zone Research Institute, Jodhpur 342003, Rajasthan, India
Central Muga Eri Research and Training Institute, Central Silk Board, Jorhat 785700, Assam, India
Central Sericultural Research and Training Institute, Central Silk Board, Mysore 570008, Karnataka, India
Indian Council of Agricultural Research, New Delhi 110001, Delhi, India
Authors to whom correspondence should be addressed.
Sustainability 2022, 14(19), 11876;
Submission received: 17 August 2022 / Revised: 16 September 2022 / Accepted: 18 September 2022 / Published: 21 September 2022


Salt-affected soils contain high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil). Globally, about 932 million ha (Mha), including 831 Mha of agricultural land, is salt-affected. Salinity and sodicity adversely affect soil microbial diversity and enzymatic activities, and thereby carbon and nitrogen dynamics and greenhouse gas (GHG) emissions from soils. In this review article, we synthesize published information to understand the impact of salinity and sodicity on GHG production and emissions from salt-affected soils, and how various reclamation amendments (gypsum, phosphogypsum, organic manure, biochar, etc.) affect GHG emissions from reclaimed soils. Nitrous oxide (N2O) and methane (CH4) emissions are of greater concern due to their 298 and 28 times higher global warming potential, respectively, compared to carbon dioxide (CO2), on a 100-year time scale. Therefore, CO2 emissions are given negligible/smaller significance compared to the other two. Generally, nitrous oxide (N2O) emissions are higher at lower salinity and reduced at higher salinity mainly due to: (a) higher ammonification and lower nitrification resulting in a reduced substrate for denitrification; (b) reduced diversity of denitrifying bacteria lowered down microbial-mediated denitrification process; and (c) dissimilatory nitrate reduction to ammonium (DNRA), and denitrification processes compete with each other for common substrate/nitrate. Overall, methane (CH4) emissions from normal soils are higher than those of salt-affected soils. High salinity suppresses the activity of both methanogens (CH4 production) and methanotrophs (CH4 consumption). However, it imposes more inhibitory effects on methanogens than methanotrophs, resulting in lower CH4 production and subsequent emissions from these soils. Therefore, reclamation of these soils may enhance N2O and CH4 emissions. However, gypsum is the best reclamation agent, which significantly mitigates CH4 emissions from paddy cultivation in both sodic and non-sodic soils, and mitigation is higher at the higher rate of its application. Gypsum amendment increases sulfate ion concentrations and reduces CH4 emissions mainly due to the inhibition of the methanogenesis by the sulfate reductase bacteria and the enhancement of soil redox potential. Biochar is also good among the organic amendments mitigating both CH4 and N2O emission from salt-affected soils. The application of fresh organic matter and FYM enhance GHG emissions for these soils. This review suggests the need for systematic investigations for studying the impacts of various amendments and reclamation technologies on GHG emissions in order to develop low carbon emission technologies for salt-affected soil reclamation that can enhance the carbon sequestration potential of these soils.

Graphical Abstract

1. Introduction

Soil salinization and sodification are serious causes of land degradation particularly in arid and semi-arid regions worldwide. Soils with high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil) are considered salt-affected soils [1]. Globally, 831 million ha (Mha) of the land of which ~20% is agricultural and ~33% is irrigated, is distributed among 120 countries and is salt-affected [2,3]. The expansion of these soils is expected to increase due to climate change, intrusion of sea water in coastal regions, and poor irrigation management in canal command areas [4]. Enhanced intensity and frequency of extreme events, particularly storms/cyclones in coastal areas, have been observed during the last 50 years [5]. Additionally, unjustifiable use of groundwater, excess use of synthetic fertilizers, and poor soil management are the causes of salt-induced soil degradation [6]. The saline (with excess salt) and alkali (with high residual alkalinity) groundwater are generally associated with the development of salt-affected lands [7]. Globally, 2400 Mha of land area (16% of total land) is underlain with the saline/alkali groundwater at the shallow/intermediate depth and the maximum area (14% of total saline/alkali water area) is found in the Basin of West and Central Asia [7]. The changing environmental scenario would further reduce the availability of good quality waters for irrigations [5], which will further enhance the utilization of marginal quality waters for irrigation and consequently enhance the expansion of area under salt-affected soil [8].
The enhanced greenhouse gas (GHG) emissions are the real cause of the greenhouse effect and agriculture contributes significantly [9] towards emissions through key processes/managements such as methane (CH4) from enteric fermentation and rice cultivation, nitrous oxide (N2O) from the application of synthetic fertilizers, and carbon dioxide (CO2) from tillage operations [10,11]. The emissions of N2O and CH4 are of greater concern due to 298 and 28 times higher global warming potential (GWP) than that of CO2 [10] on a 100-year time scale, respectively [5]. Global GHG emissions from agricultural activities were 9.3 Giga tonnes (Gt) of CO2 equivalents (CO2 eq) in 2018 [2]. The contribution of CH4 and N2O emissions from crops and livestock was 5.3 Gt CO2 eq with agricultural soils and enteric fermentation being major sources contributing 39.5 and 39.2%, respectively [2]. The emissions of CO2, CH4, and N2O occur from the agricultural soils through microbial-mediated processes/pathways. CO2 flux from agricultural soils can be due to (i) soil respiration (root and microbial respiration), (ii) ecosystem respiration, and (iii) net ecosystem exchange (NEE), i.e., the difference between plant photosynthesis and ecosystem respiration (heterotrophic, as well as autotrophic) [12]. Under anoxic conditions, CH4 is produced by methanogens and consumed by methanotrophs under oxic and anoxic conditions [10,13,14,15]. N2O is produced mainly through the denitrification process in anaerobic environments and the nitrification (hydroxylamine oxidation and nitrifier denitrification) process in aerobic environments [16,17,18].
Irrigation with saline/sodic waters induces changes in soil structure and adversely affects the microbe-mediated soil processes [19]. Generally, the excess salt in soils restricts the microbial population and their activity through osmotic stress [20]. High salt concentration in soil inhibits the soil organic matter decomposition through alteration of microbial activities leading to either decrease or increase in mineralization of carbon (C) and nitrogen (N) [21,22]. However, inhibition of N mineralization is temporary and recovers at later stages [23]. GHG emissions from soils are governed by microbial activities involved in organic matter decomposition, nitrification, denitrification, methanogenesis, and CH4 oxidation processes, and salinity and sodicity have significant effects on these processes [24]. Usually, GHG emissions decrease with increased soil salinity and sodicity. A decrease in N2O [25,26], CH4 [27,28], and CO2 [29,30] emissions with increased salinity and sodicity has been reported in several studies. However, reports on increased N2O [30], CH4 [24,31], and CO2 [31] emissions are also available. To our best knowledge, the review article concerning the N2O, CH4, and CO2 emissions from the salt-affected soils, various factors affecting their emissions, and the impacts of reclamation approaches of salt-affected soils on GHG emission has not yet been published. Therefore, the present manuscript has been organized to understand the conditions, interplaying factors along with the impact of reclamation processes on the GHG emissions from the salt-affected soils to refine the reclamation practices and ecosystem sustainability along with the climate change mitigation in these affected agro-ecosystems.

2. Salt-Affected Soils, Global Extent, and Distribution

Salt-affected soils have a high concentration of soluble salts in such a quantity that negatively affect normal growth and productivity [32]. These problematic salts are mainly carbonates (CO32−), bicarbonates (HCO3), chlorides (Cl), and sulfates (SO42−) of sodium (Na+), calcium (Ca2+), and magnesium (Mg2+) [33]. Salt-affected soils are classified into three categories, i.e., (i) saline, (ii) alkali/sodic, and (iii) saline-alkali/saline-sodic soils based on the electrical conductivity of saturated paste extract (ECe), pH of saturated paste (pHs), exchangeable sodium percentage (ESP), and sodium adsorption ratio in saturated paste extract (SARe) [33]. Saline soils contain high concentration of neutral salts mainly chlorides and sulfate of sodium, calcium and magnesium, and have ECe > 4 dS m−1, pHs < 8.5, ESP < 15, and SARe < 13 [34]. Alkali/sodic soils possess excess contents of carbonates, bicarbonate and silicate salts of sodium, and characterized by ECe < 4 dS m−1, pHs > 8.5, ESP > 15, and SARe > 13. While saline-alkali soils have high levels of both soluble salts and ESP, and these show ECe > 4 dS m−1, SARe > 13, ESP > 15, and variable pHs due to collective effects of both salinity and sodicity [35]. Detailed characteristics of salt-affected soils are given in Table 1. Globally, about 20% of agricultural land (831 Mha) is salt-affected [3]. Out of the total salt-affected soils, 47.8% (397 Mha) is saline and 52.2% (434 million ha) is sodic in nature (Figure 1). The area of these salt-affected soils is distributed in 120 countries and represents 10, 20, and 33% of the global, agricultural, and irrigated lands, respectively [33,36]. Globally, the Amu-Darya and Syr-Darya River Basins (Aral Sea Basin) in Central Asia, the Indo-Gangetic Basin in India, the Indus Basin in Pakistan, the Yellow River Basin in China, the Euphrates Basin in Syria and Iraq, the Murray-Darling Basin in Australia, and the San Joaquin Valley in the United States are the well-known regions where salinization is extensively reported [37]. The highest (~340 Mha) salt-affected area, i.e., 50% of total global sodic soils, is found in Australia, followed by Central and South Asia (~212 Mha) [38,39]. Kazakhstan (~60 Mha) and Uzbekistan (~28 Mha) are the main salinity-affecting countries in the Central Asian region [39,40]. In India, the problem extends over an area of about 6.73 Mha (2.96 Mha saline soil, and 3.77 Mha sodic soil) land, which is about 2% of India’s total geographic area (TGA) [41,42].

3. Microbial Response to Salinity and Sodicity

Soil microbial communities perform an essential role in the organic matter decomposition, nutrient cycling, and GHG production/consumption and both Soil salinity/sodicity adversely affect the microbial biomass [44] and play a decisive role in the structuring, and distribution of microbial communities [45]. Siddikee et al. [46] reported the adverse impact of soil salinity/sodicity on microbial activities and biogeochemical processes that are essential in the mineralization of nutrients. The salinity/sodicity has an extensive impact on GHG production and emissions from agricultural soils mainly due to their influences on the growth and activities of nitrifying, denitrifying, methanogen and methanotrophs. The mechanisms which may interpret the relationship between salinity/sodicity and these microorganisms are described and depicted in Figure 2. A high concentration of soluble salts inhibits microbial growth due to the adverse impact of increased osmotic stress in general and specific ion toxicity in particular [19]. Soil salinity reduces microbial activities by altering the soil’s physicochemical properties [47]. Increased sodicity decreases the O2 diffusion in the soil due to the blocking of soil pores and consequently decreases soil respiration [48]. At a high level of soil salinity, the toxicity of Cl and hydrosulfide (HS) ions caused adverse impacts on microbial growth and thereby on N2O and CH4 emissions [49].
High salinity levels inhibit the nitrification rate and decrease the availability of nitrate (NO3) which further limit the denitrification process and thereby reduces the N2O emissions [50]. Rysgaard et al. [51] reported that an increase in salinity decreases the ammonia adsorption by soil sediments which potentially enhances the availability of ammonia and thus stimulates nitrification [51]. Higher salinity limits the availability of soil organic matter/organic substrates for heterotrophic bacteria and alters the abundance and activities of microbes [52]. It also limits the biodegradation of complex organic substrates into simpler ones (H2, formate, acetate, alcohol, and other compounds) which are used by methanogens for CH4 production and thereby reduces CH4 emissions [53]. The decrease in microbial enzymes and gene activities involved in organic matter decomposition, nitrification, denitrification, methanogenesis, and CH4 oxidation has also been reported [54]. Increasing salinity enhance the ability of dissimilatory nitrate reduction to ammonium (DNRA) to overcome the denitrification [55]. Because increasing salinity enhances the population and activity of sulfate reducers [56] and consequently may increase HS ions. These HS ions have a more inhibitory effect on denitrifying bacteria than DNRA [57].
Figure 2. Response of nitrifying, denitrifying, methanogens, and methylotrophs/methanotrophs involved in GHG production and consumption to soil salinity and sodicity. Orange (nitrification, denitrification, methanogenesis, and methylotrophy), blue (nitrification/denitrification), and green (methanogenesis/methylotrophy) colors represent the GHG production process/pathways affected by salinity and sodicity.
Figure 2. Response of nitrifying, denitrifying, methanogens, and methylotrophs/methanotrophs involved in GHG production and consumption to soil salinity and sodicity. Orange (nitrification, denitrification, methanogenesis, and methylotrophy), blue (nitrification/denitrification), and green (methanogenesis/methylotrophy) colors represent the GHG production process/pathways affected by salinity and sodicity.
Sustainability 14 11876 g002

3.1. Effect of Salinity/Sodicity on Nitrification/Denitrification

3.1.1. Nitrification

Nitrification is a two-step process involving (a) ammonia oxidation regulated by ammonia-oxidizing archaea (AOA) and (b) nitrite oxidation process regulated by ammonia-oxidizing bacteria (AOB) [18]. The response of AOA and AOB to salinity level is controversial. Some studies advocated that nitrification is predominated by AOA at salinity levels up to 10–20 parts per thousand (ppt) while activities of AOB decreased at increased salinity [58]. Other investigations advocate that the activities of AOB were more than AOA at increased salinity levels [59]. These contradictory observations indicate that besides the salinity/sodicity levels other factors also affect the community structure and predominance of AOA and AOB. Slightly acidic to neutral pH and availability of ammonia favor the growth of AOB as compared to AOA [60,61]. Guo et al. [62] reported that saline water irrigation increased soil salinity and ammonical N and lower AOA/AOB ratios. Kaushik and Sethi [63] observed a significant reduction in the growth of both ammonium oxidizers and nitrite oxidizers in rice rhizosphere under increased salinity, and ammonium oxidizers were found more susceptible than nitrite oxidizers to salt stress. Magalhães et al. [64] observed a higher nitrification rate with increasing salinity from 0 to 15 ppt in the Douro River estuary. Zhou et al. [36] found that the growth and activities of nitrifiers were optimum at 5–10 ppt and excess levels of salinity (>10 ppt) showed the inhibitory effect. Overall, moderate salinity enhanced the nitrification rate while excess salinity decreases. Soil moisture is a key factor influencing nitrification and denitrification rates at higher salinity levels [65]. Denitrification had a significantly positive relationship with soil moisture and it increased with an increase in soil moisture when the soil water content was less than 27.03% and decreased with an increase in soil moisture when the soil water content was more than 27.03% [66].

3.1.2. Denitrification

Denitrification is a microbial-mediated multi-step anaerobic process in which nitrate (NO3) is sequentially reduced into nitrite (NO2), nitric oxide (NO), nitrous oxide (N2O), and finally into atmospheric nitrogen (N2) [67]. Denitrification is facilitated by a combination of four independent enzymes, i.e., nitrate reductase (NAR/NAP), nitrite reductase (NIR), NO reductase (NOR), and N2O reductase, which have been encoded by narGH/napA, nirK/nirS, nonB, and nosZ genes, respectively [68]. Denitrifying bacteria perform differentially under saline and sodic environments. Several studies advocate that soil salinization consistently reduces the denitrification [36,69]. However, Franklin et al. [52] observed an abundance of denitrifiers at low salinity (5 ppt). The negative association of denitrifiers with sediment salinity (0–36 ppt) in estuaries has been explored by Giblin et al. [50] and Santoro et al. [49]. Zhang et al. [70] envisage that increased salinity increases nitrification and denitrification below the threshold value of salinity (EC = 1.13 dS m−1) and decreases nitrification and denitrification above the threshold salinity.
Santoro et al. [49] found that the diversity of two genes nirS and nirK was negatively associated with salinity in coastal aquifers and the relative abundance of nirS was higher than nirK. This indicated the environmental effect of salinity on the metabolic performance of the microbial populations. Wang et al. [69] advocated that salinity significantly reduced the abundance of nirK, nirS, and nosZ genes and decreased the population of denitrifying bacteria. Shao et al. [71] found increased N2O efflux under >0.5% salinity conditions. Fiedler et al. [72] reported a 42 times higher abundance of nitrite reductase nirS in salt–affected soil than in controlled soil which suggests that the saline soils have a higher potential for denitrification. N2O reductase (nosZ) is more sensitive to soil salinity and depressed significantly under salinity conditions hence N2O is not reduced into N2 resulting in more N2O accumulation and effluxes from the denitrification [73]. Decoupling of nitrification or denitrification processes under saline conditions might be a possible mechanism for increasing N2O effluxes under salinity [71]. However, some other investigations also concluded that N2O emissions are negatively associated with soil salinity [74].

3.2. Effect of Salinity/Sodicity on Methanogenesis/Methanotrophs

Methanogenesis is the microbial-mediated process of CH4 production from the complex organic material by bacteria and archaea. Bacteria hydrolyze the complex organic material into simpler substrates (H2, formate, certain alcohols, acetate, etc.) which are further consumed by methanogens as food and produced CH4 [75]. Limited literature is available about the abundance and community structure of methanogens and methylotrophs in the hypersaline environment. Ollivier et al. [76] reported generation of CH4 from H2 + CO2 at salinities up to 240 ppt but not from acetate even at salinities > 60 ppt. Scholten et al. [77] investigated the abundance and distribution of methanogen-specific functional genes (mcrA) in hypersaline environments. Investigations by Bebout et al. [78] and Smith et al. [79] did not report any significant contribution of methanogenesis in carbon remineralization under a hypersaline environment. This might be due to the predominance of sulfate reducers or high oxygen concentration in a photic zone that precludes methanogenic activity from such environments under field conditions [78,79].
Heyer et al. [80] reported that the culture of methanotrophic bacteria is capable of growing to a 15% NaCl level. Nguyen et al. [81] reported very low methane emissions from paddy cultivated in salt-affected but cow manure addition enhanced CH4 emissions significantly due to improved relative abundance of methanogens by enhancing soil properties and nutrient availability. Shao et al. [71] and Xiao et al. [82] concluded that salinity imposes more inhibitory effects on methanogens than methanotrophs or methylotrophs. Low salinity favors the growth of methanogens because Na+ ions are required by methanogens for growth, amino acid transportation, methanogenesis, and internal pH regulation [83]. Weston et al. [84] investigated that acetoclastic methanogens were significantly inhibited by the in-situ addition of saline solution in the Delaware Wetland of New Jersey. However, hydrogenotrophic methanogens did not show any significant change in methanogenesis rate under the same investigation.

4. GHG Emissions from Salt-Affected Soils

4.1. Nitrous Oxide Emissions

N2O is produced through nitrification (conversion of NH4+ to NO2, and NO2 to NO3) and denitrification (conversion NO3 to N2) pathways (Figure 3a) [67]. The N2O efflux is influenced by soil pH, salt concentration, temperature, redox potential, O2 concentration, etc. Studies conducted on N2O efflux under salt-affected conditions are summarized in Table 2. N2O emissions from low salinity wetland soils (0.060 mg kg−1) were reported higher as compared to high salinity wetland soils [26]. It is reported that the addition of salts up to a certain threshold may enhance the N2O emissions and decrease thereafter [85]. The lower salinity level inhibits both the steps of nitrification (conversion of NH4+ to NO2 and NO2 to NO3), however, the inhibition of NO2 to NO3 conversion is stronger than that of NH4+ to NO2 causing higher NO2 accumulation and enhanced N2O emissions (Figure 3b) [85]. Li et al. [25] reported 110% higher N2O emissions in slightly saline soil (1.0 dS m−1) but 20% lower in moderate salinity (5 dS m−1) soil as compared to non-saline soil (0.3 dS m−1) under urea and ammonium sulfate fertilizer application. Ghosh et al. [30] observed that ammonical fertilizers, at low salinity, may enhance the N2O emissions as compared to non-saline soil because that low salinity reduces the activity of N2O reductase enzymes, therefore restricting the conversion of N2O to N2. In addition, low salinity can also serve as strong inhibition of nitrite oxidizers than ammonia oxidizers (Figure 3b) [36].
Soil moisture has a significant effect on N2O emissions from saline soil. For instance, 4.7–37.6 and 5.0–15.3 times higher N2O emissions at 100% soil moisture level than at 50 and 75% soil moisture levels, respectively, was reported by Li et al. [85], and it was mainly due to an increased rate of nitrification with increasing soil moisture [85]. Thapa et al. [86] reported that increasing salinity from 0.81 to 4.65 dS m−1 increased N2O flux at 90% of Water-filled pore space (WFPS) but reduced at 60% of WFPS in sulfate-dominated saline soil and it was due to that denitrifying bacteria performed more efficiently even at higher salinity levels because water addition reduces the adverse effect of salinity [86]. The quality of irrigation water plays important role in GHG emissions. Ma et al. [54] reported that saline water irrigation (8.01 dS m−1) significantly reduced cumulative N2O emissions than freshwater irrigation in calcareous soil. Wei et al. [87] reported that N2O emissions decreased by 29.1 and 39.2% in 2 and 8 g L−1 saline water irrigation, respectively, but increased by 58.3% in 5 g L−1 treatments under N120 conditions as compared to freshwater irrigation. This investigation envisages that the sensitivity of N2O production and consumption differed significantly with the degree of irrigation water salinities [87]. Nitrification is highly sensitive to salinity and lower N2O emissions are expected with higher salinity levels. However, few researchers also reported the reverse trends [24,27,29].
Figure 3. (a) Overview of the N2O production pathways. (b) Inhibition of nitrification pathways due to soil salinity. The lower level of soil salinity slightly inhibits the activity of ammonia-oxidizing bacteria (AOB) and strongly inhibits the activity of nitrite-oxidizing bacteria (NOB) leading to the accumulation of NO2 in soils and thereby high N2O emissions. Adopted and modified from [18,25].
Figure 3. (a) Overview of the N2O production pathways. (b) Inhibition of nitrification pathways due to soil salinity. The lower level of soil salinity slightly inhibits the activity of ammonia-oxidizing bacteria (AOB) and strongly inhibits the activity of nitrite-oxidizing bacteria (NOB) leading to the accumulation of NO2 in soils and thereby high N2O emissions. Adopted and modified from [18,25].
Sustainability 14 11876 g003
Table 2. Effect of soil salinity and sodicity on GHG emissions from saline ecosystems.
Table 2. Effect of soil salinity and sodicity on GHG emissions from saline ecosystems.
References Systems and Study LocationsTreatments DetailsObservation of the Study (GHG Emissions)Key Findings/Reasoning
Field experiments
Li et al. [25] Field experiment at Kunshan field station, Suzhou, China.Nonsaline (S0), salinity-S1 (1 dS m−1), and salinity-S5 (5 dS m−1)N2O emission increased by 89–110% at S1 and decreased by about 20% at S2. Saline soils could be a potential source of N2O emissions when cultivated. So, mitigation options should be explored.
Ma et al. [54]Long-term (2009–2018) field experiment in calcareous soil at the experimental station of Shihezi University, China.N0 (no N) + SF (fresh water, 0.35 dS m−1); N0 + SH (saline water, 8.04 dS m−1); N360 (360 kg N ha−1) + SF; N360 + SHIrrigation with saline water inhibited N2O emission, by 45.19% (N0) and 43.50% (N360) compared with irrigation with fresh waterSaline water irrigation altered community structures of denitrifying bacteria with nirK, nirS, and nosZ
Capooci et al. [31]Field experiment at temperate salt marsh connected to the Atlantic Ocean. Control (17 ppt); treatment (12.4–18.6 ppt)Soils subjected to low salinity had greater GHG emissions than control soils (17 ppt). Treatment soils had a 23% increase in GWP. The storm surges can produce pulses of GHG emissions.
Zhang et al. [88]GHG emissions from three rice (R1, R2, and R3) and maize (M1, M2, M3) fields with different salinity at Songyuan City of the Western Jilin Province, Northeast China.R1 (pH: −7.6, EC: −0.16); R2 (pH: −8.6, EC: −0.27); R3 (pH: −9.1, EC: −0.41)GWP of rice fields ranged 1070.0–1996.2 kg CO2 eq ha−1.Higher pH and salinity conditions consistently resulted in lower CO2, CH4, and N2O emissions and CH4 uptake.
M1 (pH: −7.34, EC: −0.10); M2 (pH: −7.76, EC: −0.19); M3 (pH: −8.43, EC: −0.25)GWP of maize fields ranged 600.5–1149.8 kg CO2 eq ha−1.
Poffenbarger et al. [89]Metadata analysis based on secondary in-situ studies (31 nos.) of CH4 emissions from tidal marshes Fresh (salinity < 0.5 ppt); Oligohaline (0.5–5.0 ppt); Mesohaline (5–18 ppt); Polyhaline (>18 ppt)Oligohaline marshes had the highest and most variable CH4 emissions (150 ± 221 gm−2 yr−1). Negligible CH4 emissions in polyhaline, and no significant difference between fresh and mesohaline marshes. Need to estimate or monitor CH4 emissions in lower-salinity marshes.
Laboratory experiments
She et al. [90]Laboratory experiment with different textured soil.Sandy clay loam + S1 (0.10–1.0% soil salinity); Sandy loam + S1; Silty clay + S1Cumulative CO2 emissions in the coarse-textured (sandy clay loam and sandy loam) soils were more (206–231 and 176–204 mg CO2 kg−1) affected by salinity than in the fine-textured (silty clay) soil.Soil texture controlled the negative effect of salinity on C mineralization by regulating the soil microbial community composition.
Jia et al. [26]Low salinity wetland (LW-Pragmites australis) and High salinity wetland (HW-Suaeda sals) soils were collected and incubated.LW soils (3.18 ppt salinity, 0.28 SAR); HW soils (13.30 ppt salinity, 0.03 SAR)N2O emissions were promoted in low salinity wetland (0.060 mg N2O kg−1) but significantly inhibited in high salinity wetlands (0.008 mg N2O kg−1)Study suggests the complexity and uniqueness of N2O emissions responses to nitrogen inputs related to the salinity levels.
Zhang et al. [91]Samples of saline-alkali soils were collected from four different locations in Yellow River DeltaBare land soil (no vegetation) S0 (Control); S1 (1 mg g−1); S3 (3 mg g−1); S5 (5 mg g−1)CO2 emission ranged from 88.55 (S0)–51.77 (S3) mg CO2 kg−1 and N2O 0.030 (S0)–0.012 (S3) mg N2O kg−1.The N2O and CO2 emissions of were highest in herbage communities, intermediate in woody communities, and lowest in bare land under all treatments.
The salinity effect on GHG emissions was stronger in soils with low salt levels. Higher GHG emissions at high soil moisture were found in all soils.
Land covered with woody (T. chinensis) community vegetation. CO2 emission ranged from 282.28 (S0)–231.46 (S4) mg CO2 kg−1 and N2O 0.252 (S4)–0.163 (S2) mg N2O kg−1.
Land covered with herbage (S. sals) community vegetationCO2 emission ranged from 504.33 (S0)–400.39 (S4) mg CO2 kg−1 and N2O 0.08 (S1)–0.036 (S4) mg N2O kg−1.
Land covered with herbage (P. australis) community vegetation CO2 emission ranged from 518.46 (S0)–391.27 (S4) mg CO2 kg−1 and N2O 0.153 (S1)–0.041 (S3) mg N2O kg−1.
Ghosh et al. [30]Soil samples from three different locations within a salt affected agricultural land and incubated for 30 days.S1 (0.44 dS m−1); S2 (7.20 dS m−1); S3 (4.55 dS m−1)The N2O emissions significantly increased by 39.8% and 42.4% in S2 and S3, respectively. The addition of N significantly increased cumulative N2O and CO2 emissions. Saline-sodic soils can be a significant contributor to N2O. Further, N fertilizer, irrigation, and precipitation may enhance GHG emissions.
Maucieri et al. [24]Vertisol was collected from the experimental farm of University of Sydney and incubated for 30 days.ECiw (0.09 dS m−1); ECiw (5 dS m−1); ECiw (10 dS m−1)Saline water irrigation reduced CO2 emissions by 19% (5 dS m−1) and 28% (10 dS m−1). However, N2O emissions increased by 60% with salinitySalinity decreased CO2 and increased N2O emission
Thapa et al. [86]Soil samples from Soil Health and Agriculture Research Extension (SHARE) farm were collected and incubated for 25 days.ECe < 0.50 dS m−1 (60% WFPS); ECe 4.65 dS m−1 (60% WFPS); ECe 0.81 dS m−1 (90% WFPS); ECe 4.65 dS m−1 (90% WFPS)
WFPS is a water-filled pore space
Relative decline in CO2 at higher ECe was smaller at 60% WFPS than at 90% WFPS.
N2O emission decreased by 45% at 60% WFPS and increased by 223% at 90% WFPS.
Higher soil moisture increased substrate availability, salt dilution, and enhance microbial activity, causing higher CO2 and N2O emissions.
Reddy and Crohn [29]Collected soil samples from abandoned field of Coachella Valley, California and incubated for 60 daysS3 (2.8 dS m−1) (control); S15 (15.2 dS m−1); S30 (30.6 dS m−1)Increased N2O emission by 18–24% (at S15) and 34–87% (at S30), but decreased CO2 emissions The use of active organic amendments to remediate salt-affected soils can prove to be beneficial in mitigating N2O emission
Marton et al. [27]Soil samples were collected from tidal forests along the Altamaha, Ogeechee, and Satilla Rivers in southeast Georgia and incubated in the laboratory. 0% (control); 2% saline water; 5% saline waterCH4 emission inhibited by 77% in the 2% and 89% in the 5% saline water treatment whereas
CO2 generally increased with salinity, though exhibited a variable response between the three rivers.
Short-term salinity exposure enhanced anaerobic C mineralization, a decline in CH4 production, and a varied response in N2O production
Pattnaik et al. [92]Soil samples from three locations (a) CRRI, Cuttack (alluvial soil), (b) Ernakulam, Kerala (acid sulphate saline soil (Pokkali)), and (c) Canning, West Bengal, (coastal saline soil) of India were collected and incubated for 35 days Alluvial soil (0.35 dS m−1) (control); Acid sulfate soil (5.01 dS m−1); Coastal saline soil (17.23 dS m−1)CH4 production in non-saline alluvial soil was 630.86 ng CH4 g−1, and reduce remarkably in acid sulphate saline soil (12.97 ng CH4 g−1), and coastal saline soil (142.36 CH4 g−1)High sulphate content of acid sulphate saline soil attributed to lower emission
Alluvial: (0.35 dS m−1) (control); (4 dS m−1); (8 dS m−1); (16 dS m−1); (20 dS m−1)Addition of salts to the non-saline alluvial soil at 4, 8, 16 and 20 dS m−1 progressively decreased CH4 production.CH4 inhibition due to low microbial activities and soil microbial population including that of methanogens
Pot experiments
Khatun et al. [28]Pot study in net house at Bangladesh Agricultural University, Mymersingh, BangladeshControl (100% NPK); control + 25 nM NaCl; control + 50 nM NaCl; control + 75 nM NaClDecreased yield scaled CH4 emission from 7.5% (25 nM NaCl) to 25% (75 nM NaCl)Phosphogypsum and biochar with recommended fertilizers in saline soils could mitigate yield scaled CH4 emissions
Wei et al. [87]Collected soil samples from the greenhouse of Nanjing Vegetables Scientific Institute, China, and conducted pot experiments.Freshwater (0.3 dS m−1) + N120 (120 kg N ha−1); S1 (3.5 dS m−1) + N120; S2 (8.1 dS m−1) + N120; S3 (12.7 dS m−1) + N120Irrigation with S1 water lowered N2O emission and S2 enhanced emission by 58.3%the effect degree of salinity on consumption and production of N2O might vary among irrigation salinity ranges
Reddy and Crohn [29] reported 0.004–0.007 mg N2O kg−1 soil at 2.8 dS m−1, which increased by 18–24% and 34–87% at 15.2 and 30.6 dS m−1, respectively (Table 2), mainly because of denitrification being the main process behind N2O emissions. Similarly, Maucieri et al. [24] observed higher N2O emissions from increased irrigation water salinity. Marton et al. [27] also reported higher N2O emissions from tidal forest soil in southeast Georgia irrigated with high levels of irrigation water salinities. The possible reasons behind the higher N2O emissions at higher salinity levels were (a) decoupling of either denitrification and nitrification processes [93] and (b) the higher salinity levels have increased the sulfate reduction leading to a higher concentration of H2S which is popularly known as the inhibitor for N2O reduction [94,95]. Another possible reason is that high salinity suppresses the activity of N2O reductase leading to N2O accumulation due to denitrification under a saline environment [73,96].
Overall, it can be concluded that both soil and irrigation water salinity significantly affect the N2O emissions from soils. Usually, the higher the levels of salts, the lower the N2O emissions [26,66]. Although, soil salinity is a limiting factor affecting the nitrification and denitrification processes by changing the microbial growth and activity as well as the physical and chemical properties of soil. Beside this moisture is the key factor influencing nitrification and denitrification in salt-affected soils [65]. Denitrification had a significantly positive relationship with soil moisture and it increased with an increase in soil moisture when the soil water content was less than 27.03% and decreased with an increase in soil moisture when the soil water content was more than 27.03% [66].
There are several mechanisms behind this. Firstly, high salinity stress enhances the ammonification and inhibited the nitrification process resulting in reduced NO3 and a rise in NH4+ concentration in soils, which restricted the concentration of substrate for the denitrification, the main process responsible for N2O production [66,97]. Laura [98] reported that high salinity stress completely inhibited the process of nitrification due to a decrease in the nitrifying community in the soils. Further higher ionic strength at high salinity levels can adsorb the exchangeable NH4+ ions [99]. Secondly, the diversity of denitrifying bacteria is reduced at higher salinity stress [100,101], which may lower down microbial-mediated denitrification process limiting the N2O production. Finally, at higher salinity, the dissimilatory nitrate reduction to ammonium (DNRA) and denitrification processes compete with each other for a common substrate, i.e., NO3, and thereby the rate of nitrification is limited due to the unavailability of NO3 [102]. In contrast, several researchers reported higher N2O emissions with increased salinity stress mainly due to the reduction of N2O to N2 conversion and higher N mineralization [24,36]. Jia et al. [26] reported an increased rate of denitrification with the addition of salts up to 1–5 ppt but decreased with 10 ppt salts level. Zhou et al. [103] reported a higher N2O to N2 ratio with high salinity treatments. Altogether, it is concluded that the relationship between the N2O production and salinity levels significantly depends on various processes of production and consumption/reduction of N2O under salinity stress, which is highly variable with variations in levels of salinity, moisture, soil pH, and concentration of NO3 and NH4+, etc. in soils.

4.2. Methane Emissions

Methane is produced by methanogenic bacteria/archaea (methanogens) as the end product of organic matter decomposition under anaerobic conditions [104,105]. Under an anaerobic atmosphere, methanogens utilize the methanogenic substrates (methanol, formate, acetate, and CO2) produced due to organic matter decomposition by a range of heterotrophic organisms (Figure 4) [13]. CH4 is consumed by methanotrophs as a source of energy and carbon and they can grow both in aerobic and anaerobic environments [10,15]. Several factors such as pH, salt concentration, redox potential, soil organic matter, microbial community, etc. affect the CH4 emissions from soils [10,106]. Soil pH and salt concentration significantly affect the methane emissions from soils and generally, it is inversely related to the salinity/sodicity. Usually, CH4 emissions from normal/non-saline soil are higher as compared to saline and sodic soil [28,107]. CH4 emissions reported from the saline soils of different ecosystems are given in Table 2. Sun et al. [108] reported 71% higher CH4 emissions from non-saline inland soils than that from coastal soil in a meta-analysis. Datta et al. [109] reported similar results from a field experiment in India. They reported higher CH4 emissions (279.79–378.20 kg CH4 ha−1) from non-saline soil as compared to saline soil (123.87–170.46 kg CH4 ha−1) under similar management practices. The findings of Sun et al. [108] and Datta et al. [109] suggest that higher concentrations of exchangeable cations (Na+, K+, Ca2+, and Mg2+) were the main reason behind the lower CH4 emissions from saline soils. High soil salinity suppresses the activity of methanogens resulting in lower CH4 production and subsequent emissions [110,111,112,113].
Recently, Khatun et al. [28] reported an inverse relationship between salinity stress and CH4 emissions and CH4 emissions were 6.6, 6.1, 5.6, and 4.9 g CH4 pot−1 season−1 with 0, 25, 50, and 75 mM NaCl stress, respectively. In China, Zhang et al. [88] investigated CH4 emissions from rice soil reduced significantly by about 16 and 39 in 0.27 and 0.41% salinity levels, respectively, as compared to the 0.16% salinity (Table 2). The higher salinity levels inhibited the CH4 oxidation potential of methanotrophs resulting in higher CH4 emissions over lower salinity levels [88]. Marton et al. [27] collected tidal forest soils from three different locations and incubated them in the laboratory with 0, 2, and 5% salinity levels of irrigation water and reported that CH4 emissions decreased from 0.51 to 0.07 mg CH4 kg−1 h−1 by increasing salinity from 0 to 5% (Table 2).
Pattnaik et al. [92] reported significantly higher (3.78 mg CH4 kg−1 soil) mean CH4 emissions from non-saline alluvial soil as compared to acid sulfate soil (0.02 mg CH4 kg−1 soil). The major reason behind this was the high sulfate content of acid sulfate soil which enhances the population of sulfate-reducing bacteria (SRB), and these SRB compete with the methanogens for common substrates (Figure 4) [110]. CH4 emissions were significantly lower in the coastal saline soil (0.25 mg CH4 kg−1 soil) as compared to non-saline alluvial soil (3.78 mg CH4 kg−1 soil), which was mainly due to the higher salt content of coastal saline soils. Further, the non-saline alluvial soil was incubated with different levels of salinity, and it was reported that inhibition of the CH4 production was directly proportional to the salinity levels. The average CH4 emissions were reduced by 55% at 4 dS m−1 salinity and almost inhibited at the 20 dS m−1 salinity. Maucieri et al. [24] and Zhang et al. [88] reported that a higher level of soil salinity reduces the CH4 uptake by methanotrophs. Zhang et al. [88] studied the CH4 uptake/emissions from three maize fields (M1, M2, and M3) having different salinity and sodicity levels. The cumulative CH4 uptake was 0.77 kg CH4 ha−1 from M1 (pH: −7.34, EC: −0.10), and it was reduced by 16% and 24% in the case of M2 (pH: −7.76, EC: −0.19) and M3 (pH: −8.43, EC: −0.25) soils. Similarly, Maucieri et al. [24] collected soil samples in pots and studied the CH4 uptake/emissions by irrigating with three types of saline water (0.5/0.9, 5.0, and 10 dS m−1). Total CH4 uptake/emissions was 0.07, 0.07, and 0.06 mg CH4 kg−1 soil in 0.9, 5.0, and 10 dS m−1, respectively. Earlier Poffenbarger et al. [89] did the metadata analysis for CH4 emissions from tidal marshes [fresh (salinity < 0.5 ppt), oligohaline (0.5–5.0 ppt), mesohaline (5–18 ppt), and polyhaline (>18 ppt)] and reported that CH4 emissions from the fresh, oligohaline, mesohaline, and polyhaline marshes were 419, 1500, 164 and 11.2 kg ha−1 year−1. Generally, CH4 emissions decreased with increased salinity of tidal marshes, however, there is a need to monitor or estimate the CH4 emissions from oligohaline marshes.
Figure 4. Schematic diagram showing the process of CH4 production, mechanism of reduction of CH4 production with the application of gypsum and phosphogypsum through competition with the sulfate-reducing bacteria, Modified from [114,115].
Figure 4. Schematic diagram showing the process of CH4 production, mechanism of reduction of CH4 production with the application of gypsum and phosphogypsum through competition with the sulfate-reducing bacteria, Modified from [114,115].
Sustainability 14 11876 g004

4.3. Carbon Dioxide Emissions

Both salinity and sodicity induce a significant impact on CO2 emissions from soils and usually, CO2 emissions have an inverse relation with salinity [90,111] and a positive relationship with soil temperature. Recently, Yu et al. [116] studied the process of CO2 emissions under different levels of soil salinity and temperature and observed a positive correlation between CO2 emissions, soil salinity, and temperature [116]. Soil temperature significantly affects the microbial population prevailing in the saline soil (Figure 5). At higher temperatures gram-positive bacterial and fungal populations dominated in the saline soil and these microbial populations effectively decomposed soil organic carbon pool into CO2 [117]. She et al. [90] studied the effect of salinity levels on CO2 emissions and found that under similar salinity levels (0.10–1.0%), the highest CO2 emissions were reported from sandy clay loam soil (206–231 mg CO2 kg−1 day−1) followed by sandy loam and lowest from silty clay. Zhang et al. [91] collected soils from four different soils having different salinity and vegetation types, i.e., bare soil (EC: 14.84 mS cm−1), T. chinensis community (EC: 10.46 mS cm−1), S. salsa community (EC: 5.18 mS cm−1), and P. australis community (EC: 2.47 mS cm−1). They incubated these soils with four salinity levels as control, 1 mg g−1, 3 mg g−1, and 5 mg g−1. CO2 emissions from the bare land were the lowest (51.76 to 88.55 mg kg−1 soil). Whereas CO2 emissions, from the soils with communities of T. chinensis, S. salsa, and P. australis: were from 231.46 to 282.25, 400.39 to 504.33, and 391.27 to 518.46 mg kg−1 soil, respectively (Table 2). CO2 emissions from the same soils with different salinity levels were decreased with increased salinity. It was observed that the CO2 emissions from these soils were positively correlated with available labile soil carbon [91]. Degradation of above and below-ground biomass enhanced the labile carbon which results in higher CO2 emissions from salt-affected soil with vegetation cover than bare salt-effected soil. Maucieri et al. [24] incubated the Vertisol soil in the laboratory adjusting irrigation water salinity to 0.09, 5.0, and 10.0 dS m−1 using NaCl and studied GHG emissions. They reported that with increasing salinity, CO2 emissions decreased by 19% (5 dS m−1) and 28% (10 dS m−1) as compared to control (0.09 dS m−1). Reddy and Crohn [29] collected soil samples from Coachella Valley, California having three different levels of ECe (2.8, 15.2, and 30.6 dS m−1) and measured CO2 emissions in an incubation experiment and reported 70–371 mg CO2 kg−1 soil in 2.8 dS m−1, 38–259 mg CO2 kg−1 soil in 15.2 dS m−1, and 12.47–187 mg CO2 kg−1 soil in 30.6 dS m−1 salinity level.

5. Impact of Soil Amendments on GHG Emissions from Salt-Affected Soils

Reclamation and sustainable management of salt-affected soils for economic production of crops is a global challenge and expected climate change has further aggravated the task. Several management practices including gypsum, phosphogypsum, organic matter, biochar, vermicompost, etc. were evaluated and promoted for the management of these soils (Table 3). These amendments are being used to improve salt-affected soils for agricultural performance. Besides, they also have an impact on soil microbial activities and thus may enhance or reduce GHG emissions. Therefore, the impact of various reclamation technologies/materials on GHG emissions needs a global scientific investigation.

5.1. Impact of Gypsum and Phosphogypsum Application on GHG Emissions

Gypsum and phosphogypsum are used for centuries to reclaim alkali soils. Once gypsum dissociates into calcium and sulfur, calcium has the greatest attraction for the soil particle displacing sodium and helps flocculate (aggregate) the soils to improve soil structure. Besides, it might also affect the soil microbes involved in GHG emissions. Several literatures are available on the gypsum application and reclamation of alkali soils. However, very selective studies are available that assessed the effect of these soil corrections on GHG emissions. Some studies [28,83,118] studied the CH4 emissions in the rice ecosystems and observed its mitigation in reclaimed soils. Denier van der Gon and Neue, [127] reported 55–70% lower CH4 emissions from gypsum amended rice fields and it is most likely due to the inhibition of the methanogenesis by the sulfate reductase bacteria (SRB) (Table 4). Gypsum application enhance SO42− concentration, which gives rise to the competition of SRB with the methanogens for common substrate (H2, CO2, acetate) that otherwise be used by methanogens [127,128] as SRB has a high affinity for H2 and acetate as compared to methanogens [129]. This inhibition of methanogenesis by SRB is incomplete and a considerable amount of CH4 emissions still occurred [127]. The gypsum and phosphogypsum improve water infiltration through betterment in structure, thereby enhancing soil redox potential (less negative redox potential) and mitigating CH4 emissions from saline/sodic soils [28]. The rate of gypsum application also plays a significant role in CH4 emissions. Theint et al. [83] reported that CH4 emissions from alkali soils significantly increased with the application of a lower dose (0.5 t ha−1) of gypsum as rhizospheric exudates provide a sufficient amount of Organic C for methanogenesis. However, a higher dose (2 t ha−1) reduced the CH4 emissions by lowering the soil pH and increased sulfate concentration. The CH4 mitigation is generally higher with the higher dose of gypsum application, and it is because of higher competition between SRB and methanogens at a higher rate. One mole of SO42− is required for the reduction of one mole of CH4 [130]. Overall, it can be concluded that gypsum is the best reclamation agent which can be used as a mitigating agent for CH4 emissions from paddy cultivation in both sodic and non-sodic soils and mitigation is higher at a higher rate of application. Park et al. [131] reported about 60% CH4 mitigation from paddy soils with the application of 8 MG ha−1 by-product gypsum fertilizer (BGF) application. Similarly, Ali et al. [132] reported 18–23% CH4 mitigation from the coastal paddy soils with the application of silicate slag (150 kg ha−1). Both BGF and silicate slag had high free iron oxide and SO42− content which acted as electron acceptors. Sun et al. [118] explored the potential of gypsum and humic acid on CH4 and N2O emissions from coastal saline soils and recorded mitigation of 19.36% CH4 emissions and 9.43% N2O emissions in gypsum amended N fertilized soils (Table 4). The application of humic acid in coastal saline soil served as electron acceptors, which result in higher CH4 emissions as compared to no application of humic acid in soils. Further, the application of humic acid enhanced the soil redox potential which stimulate the higher N2O fluxes from the soils [118].

5.2. Organic Amendments and GHG Emissions

Organic manure, green manure, biochar, compost, etc. are commonly used for the management of salt-affected soils and biochar has a great potential for N2O mitigation [24,136]. The application of fresh organic matter and biochar improves soil’s physical, chemical, and biological properties and can either enhance or mitigate N2O emissions [29,136]. Application of fresh organic matter (crop residue, manure, FYM) increases cumulative N2O emissions due to enhanced nitrogen mineralization [137]. However, biochar application in saline soils inhibits the nitrification process through adsorption of substrate, i.e., NH3/NH4+ and resulting in a lowering of N2O emissions [24,138]. Biochar at the rate of 1% of total N in saline-alkali soil reduced nirK and nirS gene copies of denitrifiers bacteria and resulted in low N2O emissions [115]. The age of the biochar is also important in GHG mitigation, aged biochar further decreases N2O emissions from saline soils. Therefore, aged biochar could be a better option for the mitigation of N2O emissions from these soils.
Substituting inorganic fertilizer with organic matter in optimum portion can be useful in maintaining SOC in agricultural soil along with CH4 mitigation [15,139,140]. The application of biochar significantly enhanced the community structure and abundance of methanotrophs which reduces the net CH4 emissions from biochar-treated soils [136,141]. The application of FYM in rice grown in saline soil significantly enhances the population of methanotrophs [142]. Similarly, the use of FYM along with pyrite in alkaline paddy soil enhances the methanotroph population and CH4 oxidation thereby reducing seasonal CH4 emissions [142]. Wang et al. [143] reported three to six times higher methanotroph population and lower CH4 emissions with the use of biochar along with steel slag. Nguyen et al. [81] observed that cow manure addition to salt-affected soil enhanced CH4 emissions by 801%, however, the addition of biochar to cow manure amended soil reduced CH4 emissions from 28 to 680%. The application of cow manure alone enhanced the population of methanogens leading to significantly higher CH4 emissions. While application of biochar along with cow manure enhanced the methanotrophs population and thereby improved the net balance of methanogens (CH4 production) and methanotrophs (CH4 consumption) resulting in lowering the CH4 fluxes from biochar + cow manure amended soils [10,81].
Sesbania aculeate and Ipomoea lacunose green manure reduced CH4 emissions by 23.15 and 29.89%, respectively, as compared to urea application during the wet season (Table 4). However, this green manure enhanced CH4 emissions by 382.68, and 300.57%, respectively, during the dry season [109] because the higher temperature in the dry season accelerates the process of fresh green manure. Maucieri et al. [24] reported 10% lower cumulative CO2 emissions and 12% lower N2O emissions from biochar amended soil as compared to without biochar amended soil. Supparattanapan et al. [144] conducted a field experiment in a saline patch (14.2 dS m−1) and outside saline patch (4.7 dS m−1) of a single field and reported that the addition of rice straw and cow manure enhanced the CH4 emissions from both saline and outside saline patch over control. However, increased CH4 emissions were higher from the outside saline patch (153–161%) as compared to the saline patch (33–19.5%). Overall, it can be concluded that biochar can be used as the best organic amendment for mitigation of N2O and CH4 emissions from both normal soils as well as salt-affected soils.

5.3. Other Interventions for GHG Mitigation from Saline-Sodic Soils

Several other materials were also tested for the GHG mitigation potential from the salt-affected Soils. Li et al. [126] investigated the role of 3,4-Dimethylpyrazole phosphate (DMPP) a new nitrification inhibitor in reducing N2O emissions from saline soil and reported that the application of DMPP in non-saline, low saline, and high saline soil significantly reduced N2O emissions by 61.19, 74.94, and 48.82%, respectively, over non DMPP treatment (Table 4). DMPP application reduced the NO2-N accumulation and suppressed nitrifier denitrification processes and causes a lower N2O emissions [126]. Sun et al. [108] reported that the application of an acid chemical (trade name—Hekang) at the rate of 22.5 kg ha−1 along with urea application at the rate of 300 kg N ha−1 did not reduce N2O emissions from the saline soil but reduced the yield scaled emissions.

6. Future Research Directions

Based on the literature reviewed following thrust areas are identified which required future research attention for the low carbon/GHG emissions and sustainable crop production from the salt-affected lands/soils.
  • The Impacts of excess salts and high pH on GHG emissions from salt-affected soils are well documented. However, impacts of the individual ion toxicity on microbial population, enzymatic activities, and GHG production processes required further investigation.
  • Mostly, studies are conducted in the pot and laboratory under controlled conditions. However, in real field conditions the emissions may be affected by several other parameters, therefore, how salinity and sodicity in actual field conditions affect the soil GHG emissions needs further investigation.
  • How the other parameters such as soil carbon and nitrogen level, soil moisture, redox potential, precipitation, temperature, cyclones, etc. affect the seasonal variation of GHG emission from salt-affected soils before and after reclamation needs systematic investigation.
  • Systematic investigations are needed to understand and quantify the effect of different amendments and reclamation technologies such as gypsum, phosphogypsum, organic manure, green manure, biochar, etc. on GHG emissions from these soils to develop the low carbon emission reclamation technologies for the management of salt-affected soils.

7. Conclusions

Salinity and sodicity not only affect the soil’s physicochemical properties but also significantly affects the CH4, N2O, and CO2 emissions from the soil. The production of GHG in the soil is mainly governed by the microbial-mediated processes in which several organisms are involved. Salinity and sodicity have detrimental impacts on the microbial population of nitrifying, denitrifying, methanogens, methanotrophs, etc., and enzymatic activities involved in GHG production and consumption. The magnitude of its impact depends on the level of salinity and sodicity. Microbial population and soil enzyme activities are generally decreased with increasing soil salinity and sodicity which restrict the C and N mineralization and thereby GHG emissions. Generally, CH4 production and emissions from soils decrease with increasing soil salinity which is mainly due to the inhibition of methanogens activity. Similarly, N2O emissions also decreased with increasing salinity due to strong inhibition of both steps of nitrification. However, N2O emission enhanced at lower levels of salinity as compared to non-saline soils. Reclamation of salt-affected soils using various amendments normalizes the soil pH and reduces soil salinity which is favorable for the microbial population and can enhance GHG emissions from soils. However, reclamation of salt-affected soils using gypsum and phosphogypsum reduces the CH4 emissions from soils mainly through the competition due to sulfate-reducing bacteria for the common substrates. The rate of gypsum application has a greater impact on CH4 mitigation from salt-affected soils. Similarly, biochar amendments to soil reduce both CH4 and N2O emissions and mitigation is higher with aged biochar. The application of fresh organic matter and FYM may enhance GHG emissions. Although, the amendments and reclamation technologies are used to make crop cultivation possible from these soils. However, systematic investigations are needed for studying the impacts of various reclamation technologies on GHG emissions so that low carbon emissions reclamation technologies can be promoted in the policies for the reclamation of salt-affected soils, and the carbon sequestration potential of these soils can be explored.

Author Contributions

Conceptualization, R.K.F.; methodology, R.K.F. and S.K.M.; formal analysis, R.K.F. and S.K.M.; writing—original draft preparation, R.K.F., S.K.M. and D.S.; writing—review and editing, A.K., R.K.Y., P.C.S. and H.P. All authors have read and agreed to the published version of the manuscript.


This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.


The authors are grateful to the Prioritization, Monitoring and Evaluation (PME) cell of ICAR-CSSRI, Karnal, for approval of the manuscript (Review article/21/2021). We are thankful to the Editor and the three anonymous reviewers for their constructive and insightful comments which improved the quality of the manuscript a lot.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Ding, Z.; Koriem, M.A.; Ibrahim, S.M.; Antar, A.S.; Ewis, M.A.; He, Z.; Kheir, A.M.S. Seawater Intrusion Impacts on Groundwater and Soil Quality in the Northern Part of the Nile Delta, Egypt. Environ. Earth Sci. 2020, 79, 313. [Google Scholar] [CrossRef]
  2. FAOSTAT. Food and Agriculture Organization of the United Nations, Rome, Italy. 2020. Available online: (accessed on 4 April 2022).
  3. Amini, S.; Ghadiri, H.; Chen, C.; Marschner, P. Salt-Affected Soils, Reclamation, Carbon Dynamics, and Biochar: A Review. J. Soils Sediments 2016, 16, 939–953. [Google Scholar] [CrossRef]
  4. Snoussi, M.; Ouchani, T.; Niazi, S. Vulnerability Assessment of the Impact of Sea-Level Rise and Flooding on the Moroccan Coast: The Case of the Mediterranean Eastern Zone. Estuar. Coast. Shelf Sci. 2008, 77, 206–213. [Google Scholar] [CrossRef]
  5. IPPC IPCC (Intergorvernmental Panel on Climate Change). Synthesis Report 5; IPPC IPCC (Intergorvernmental Panel on Climate Change): Geneva, Switzerland, 2014. [Google Scholar]
  6. Nouri, H.; Chavoshi Borujeni, S.; Nirola, R.; Hassanli, A.; Beecham, S.; Alaghmand, S.; Saint, C.; Mulcahy, D. Application of Green Remediation on Soil Salinity Treatment: A Review on Halophytoremediation. Process Saf. Environ. Prot. 2017, 107, 94–107. [Google Scholar] [CrossRef]
  7. van Weert, F.; van der Gun, J.; Reckman, J. Global Overview of Saline Groundwater Occurrence and Genesis (Report Number: GP 2009-1). Utr. IGRAC—U. N. Int. Groundw. Resour. Assess. Cent. 2009, 1–32. [Google Scholar]
  8. Shani, U.; Dudley, L.M. Field Studies of Crop Response to Water and Salt Stress. Soil Sci. Soc. Am. J. 2001, 65, 1522–1528. [Google Scholar] [CrossRef]
  9. Tubiello, F.N.; Salvatore, M.; Rossi, S.; Ferrara, A.; Fitton, N.; Smith, P. The FAOSTAT Database of Greenhouse Gas Emissions from Agriculture. Environ. Res. Lett. 2013, 8. [Google Scholar] [CrossRef]
  10. Malyan, S.K.; Bhatia, A.; Kumar, A.; Gupta, D.K.; Singh, R.; Kumar, S.S.; Tomer, R.; Kumar, O.; Jain, N. Methane Production, Oxidation and Mitigation: A Mechanistic Understanding and Comprehensive Evaluation of Influencing Factors. Sci. Total Environ. 2016, 572, 874–896. [Google Scholar] [CrossRef] [PubMed]
  11. Fagodiya, R.K.; Pathak, H.; Kumar, A.; Bhatia, A.; Jain, N. Global Temperature Change Potential of Nitrogen Use in Agriculture: A 50-Year Assessment. Sci. Rep. 2017, 7, 1–8. [Google Scholar] [CrossRef] [PubMed]
  12. Oertel, C.; Matschullat, J.; Zurba, K.; Zimmermann, F.; Erasmi, S. Greenhouse Gas Emissions from Soils—A Review. Chemie Der Erde—Geochem. 2016, 76, 327–352. [Google Scholar] [CrossRef]
  13. Conrad, R. Microbial Ecology of Methanogens and Methanotrophs. Adv. Agron. 2007.
  14. Conrad, R. Methane Production in Soil Environments—Anaerobic Biogeochemistry and Microbial Life between Flooding and Desiccation. Microorganisms 2020, 8, 881. [Google Scholar] [CrossRef]
  15. Malyan, S.K.; Bhatia, A.; Tomer, R.; Harit, R.C.; Jain, N.; Bhowmik, A.; Kaushik, R. Mitigation of Yield-Scaled Greenhouse Gas Emissions from Irrigated Rice through Azolla, Blue-Green Algae, and Plant Growth–Promoting Bacteria. Environ. Sci. Pollut. Res. 2021. [Google Scholar] [CrossRef] [PubMed]
  16. Fagodiya, R.K.; Pathak, H.; Bhatia, A.; Jain, N.; Kumar, A.; Malyan, S.K. Global Warming Impacts of Nitrogen Use in Agriculture: An Assessment for India since 1960. Carbon Manag. 2020, 11, 291–301. [Google Scholar] [CrossRef]
  17. Ussiri, D.; Lal, R. Soil Emission of Nitrous Oxide and Its Mitigation. Soil Emiss. Nitrous Oxide its Mitig. 2013, 1–28. [Google Scholar] [CrossRef]
  18. Kumar, A.; Medhi, K.; Fagodiya, R.K.; Subrahmanyam, G.; Mondal, R.; Raja, P.; Malyan, S.K.; Gupta, D.K.; Gupta, C.K.; Pathak, H. Molecular and Ecological Perspectives of Nitrous Oxide Producing Microbial Communities in Agro-Ecosystems. Rev. Environ. Sci. Biotechnol. 2020, 19, 717–750. [Google Scholar] [CrossRef]
  19. Yan, N.; Marschner, P.; Cao, W.; Zuo, C.; Qin, W. Influence of Salinity and Water Content on Soil Microorganisms. Int. Soil Water Conserv. Res. 2015, 3, 316–323. [Google Scholar] [CrossRef]
  20. Yemadje, P.L.; Chevallier, T.; Guibert, H.; Bertrand, I.; Bernoux, M. Wetting-Drying Cycles Do Not Increase Organic Carbon and Nitrogen Mineralization in Soils with Straw Amendment. Geoderma 2017, 304, 68–75. [Google Scholar] [CrossRef]
  21. Wang, S.; Tang, J.; Li, Z.; Liu, Y.; Zhou, Z.; Wang, J.; Qu, Y.; Dai, Z. Carbon Mineralization under Different Saline-Alkali Stress Conditions in Paddy Fields of Northeast China. Sustainability 2020, 12, 2921. [Google Scholar] [CrossRef]
  22. Wichern, F.; Islam, M.R.; Hemkemeyer, M.; Watson, C.; Joergensen, R.G. Organic Amendments Alleviate Salinity Effects on Soil Microorganisms and Mineralisation Processes in Aerobic and Anaerobic Paddy Rice Soils. Front. Sustain. Food Syst. 2020, 4. [Google Scholar] [CrossRef]
  23. Khoi, C.M.; Guong, V.T.; Merckx, R. Predicting the Release of Mineral Nitrogen from Hypersaline Pond Sediments Used for Brine Shrimp Artemia Franciscana Production in the Mekong Delta. Aquaculture 2006, 257, 221–231. [Google Scholar] [CrossRef]
  24. Maucieri, C.; Zhang, Y.; McDaniel, M.D.; Borin, M.; Adams, M.A. Short-Term Effects of Biochar and Salinity on Soil Greenhouse Gas Emissions from a Semi-Arid Australian Soil after Re-Wetting. Geoderma 2017, 307, 267–276. [Google Scholar] [CrossRef]
  25. Li, Y.; Xu, J.; Liu, S.; Qi, Z.; Wang, H.; Wei, Q.; Gu, Z.; Liu, X.; Hameed, F. Salinity-Induced Concomitant Increases in Soil Ammonia Volatilization and Nitrous Oxide Emission. Geoderma 2020, 361, 114053. [Google Scholar] [CrossRef]
  26. Jia, J.; Bai, J.; Wang, W.; Yin, S.; Zhang, G.; Zhao, Q.; Wang, X.; Liu, X.; Cui, B. Salt Stress Alters the Short-Term Responses of Nitrous Oxide Emissions to the Nitrogen Addition in Salt-Affected Coastal Soils. Sci. Total Environ. 2020, 742, 140124. [Google Scholar] [CrossRef]
  27. Marton, J.M.; Herbert, E.R.; Craft, C.B. Effects of Salinity on Denitrification and Greenhouse Gas Production from Laboratory-Incubated Tidal Forest Soils. Wetlands 2012, 32, 347–357. [Google Scholar] [CrossRef]
  28. Khatun, L.; Ali, M.A.; Sumon, M.H. Mitigation Rice Yield Scaled Methane Emission and Soil Salinity Stress with Feasible Soil Amendments. J. Agric. Chem. Environ. 2021, 10, 16–36. [Google Scholar] [CrossRef]
  29. Reddy, N.; Crohn, D.M. Effects of Soil Salinity and Carbon Availability from Organic Amendments on Nitrous Oxide Emissions. Geoderma 2014, 235–236, 363–371. [Google Scholar] [CrossRef]
  30. Ghosh, U.; Thapa, R.; Desutter, T.; He, Y.; Chatterjee, A. Saline–Sodic Soils: Potential Sources of Nitrous Oxide and Carbon Dioxide Emissions? Pedosphere 2017, 27, 65–75. [Google Scholar] [CrossRef]
  31. Capooci, M.; Barba, J.; Seyfferth, A.L.; Vargas, R. Experimental Influence of Storm-Surge Salinity on Soil Greenhouse Gas Emissions from a Tidal Salt Marsh. Sci. Total Environ. 2019, 686, 1164–1172. [Google Scholar] [CrossRef] [PubMed]
  32. Rengasamy, P. Soil Salinity and Sodicity. In Growing Crops with Reclaimed Wastewater; Siro Publishing: Clayton, VIC, Australia, 2006; pp. 125–138. [Google Scholar]
  33. Rengasamy, P. Soil Processes Affecting Crop Production in Salt-Affected Soils. Funct. Plant Biol. 2010, 37, 613–620. [Google Scholar] [CrossRef]
  34. Richards, L. Diagnosis and Improvement of Saline and Alkaline Soils. Soil Sci. Soc. Am. J. 1954, 18, 348. [Google Scholar] [CrossRef]
  35. Rengasamy, P. Transient Salinity and Subsoil Constraints to Dryland Farming in Australian Sodic Soils: An Overview. Aust. J. Exp. Agric. 2002, 42, 351–361. [Google Scholar] [CrossRef]
  36. Zhou, M.; Butterbach-Bahl, K.; Vereecken, H.; Brüggemann, N. A Meta-Analysis of Soil Salinization Effects on Nitrogen Pools, Cycles and Fluxes in Coastal Ecosystems. Glob. Chang. Biol. 2017, 23, 1338–1352. [Google Scholar] [CrossRef] [PubMed]
  37. Qadir, M.; Quillérou, E.; Nangia, V.; Murtaza, G.; Singh, M.; Thomas, R.J.; Drechsel, P.; Noble, A.D. Economics of Salt-Induced Land Degradation and Restoration. Nat. Resour. Forum 2014, 38, 282–295. [Google Scholar] [CrossRef]
  38. Shahid, S.A.; Zaman, M.; Heng, L. Soil Salinity: Historical Perspectives and a World Overview of the Problem. Guidel. Salin. Assess. Mitig. Adapt. Using Nucl. Relat. Tech. 2018, 43–53. [Google Scholar] [CrossRef]
  39. Issanova, G.T.; Abuduwaili, J.; Mamutov, Z.U.; Kaldybaev, A.A.; Saparov, G.A.; Bazarbaeva, T.A. Saline Soils and Identification of Salt Accumulation Provinces in Kazakhstan. Arid Ecosyst. 2017, 7, 243–250. [Google Scholar] [CrossRef]
  40. Toderich, K.; Ismail, S.; Massino, I.; Wilhelm, M.; Yusupov, S.; Kuliev, T. Extent of Salt-Affected Land in Central Asia: Biosaline Agriculture and Utilization of the Salt-Affected Resources; KIER Working Papers 648; Kyoto University, Institute of Economic Research: Kyoto, Japan, 2018. [Google Scholar]
  41. NRSA Salt Affected Soils, National Remote Sensing Agency, Department of Space, Government of India, Hyderabad; National Remote Sensing Agency, Department of Space, Government of India: Hyderabad, India, 1997.
  42. Singh, G.; Bundela, D.S.; Sethi, M.; Lal, K.; Kamra, S.K. Remote Sensing and Geographic Information System for Appraisal of Salt-Affected Soils in India. J. Environ. Qual. 2010, 39, 5–15. [Google Scholar] [CrossRef]
  43. FAO; ITPS. Status of the World’s Soil Resources; FAO: Rome, Italy, 2015. [Google Scholar]
  44. Yuan, B.C.; Li, Z.Z.; Liu, H.; Gao, M.; Zhang, Y.Y. Microbial Biomass and Activity in Salt Affected Soils under Arid Conditions. Appl. Soil Ecol. 2007, 35, 319–328. [Google Scholar] [CrossRef]
  45. Behera, P.; Mahapatra, S.; Mohapatra, M.; Kim, J.Y.; Adhya, T.K.; Raina, V.; Suar, M.; Pattnaik, A.K.; Rastogi, G. Salinity and Macrophyte Drive the Biogeography of the Sedimentary Bacterial Communities in a Brackish Water Tropical Coastal Lagoon. Sci. Total Environ. 2017, 595, 472–485. [Google Scholar] [CrossRef]
  46. Siddikee, M.A.; Tipayno, S.C.; Kim, K.; Chung, J.; Sa, T. Influence of Varying Degree of Salinity-Sodicity Stress on Enzyme Activities and Bacterial Populations of Coastal Soils of Yellow Sea, South Korea. J. Microbiol. Biotechnol. 2011, 21, 341–346. [Google Scholar] [CrossRef]
  47. Li, C.; Lei, J.; Zhao, Y.; Xu, X.; Li, S. Effect of Saline Water Irrigation on Soil Development and Plant Growth in the Taklimakan Desert Highway Shelterbelt. Soil Tillage Res. 2015, 146, 99–107. [Google Scholar] [CrossRef]
  48. Bhullar, R.S.; Mavi, M.S.; Choudhary, O.P. Adverse Impact of Sodicity on Soil Functions Can Be Alleviated through Addition of Rice Straw Biochar. Commun. Soil Sci. Plant Anal. 2019, 50, 2369–2383. [Google Scholar] [CrossRef]
  49. Larsen, L.; Moseman, S.; Santoro, A.E.; Hopfensperger, K.; Burgin, A. A Complex-Systems Approach to Predicting Effects of Sea Level Rise and Nitrogen Loading on Nitrogen Cycling in Coastal Wetland. Eco-DAS VIII 2010, 67–92. [Google Scholar] [CrossRef]
  50. Giblin, A.E.; Weston, N.B.; Banta, G.T.; Tucker, J.; Hopkinson, C.S. The Effects of Salinity on Nitrogen Losses from an Oligohaline Estuarine Sediment. Estuaries Coasts 2010, 33, 1054–1068. [Google Scholar] [CrossRef]
  51. Rysgaard, S.; Thastum, P.; Dalsgaard, T.; Christensen, P.B.; Sloth, N.P. Effects of Salinity on NH4+ Adsorption Capacity, Nitrification, and Denitrification in Danish Estuarine Sediments. Estuaries 1999, 22, 21–30. [Google Scholar] [CrossRef]
  52. Franklin, R.B.; Morrissey, E.M.; Morina, J.C. Changes in Abundance and Community Structure of Nitrate-Reducing Bacteria along a Salinity Gradient in Tidal Wetlands. Pedobiologia 2017, 60, 21–26. [Google Scholar] [CrossRef]
  53. Oren, A. Anaerobic Degradation of Organic Compounds at High Salt Concentrations. Antonie Van Leeuwenhoek 1988, 54, 267–277. [Google Scholar] [CrossRef]
  54. Ma, L.; Guo, H.; Min, W. Nitrous Oxide Emission and Denitrifier Bacteria Communities in Calcareous Soil as Affected by Drip Irrigation with Saline Water. Appl. Soil Ecol. 2019, 143, 222–235. [Google Scholar] [CrossRef]
  55. Marchant, H.K.; Lavik, G.; Holtappels, M.; Kuypers, M.M.M. The Fate of Nitrate in Intertidal Permeable Sediments. PLoS ONE 2014, 9, e104517. [Google Scholar] [CrossRef] [PubMed]
  56. Tong, C.; She, C.X.; Yang, P.; Jin, Y.F.; Huang, J.F. Weak Correlation Between Methane Production and Abundance of Methanogens Across Three Brackish Marsh Zones in the Min River Estuary, China. Estuaries Coasts 2015, 38, 1872–1884. [Google Scholar] [CrossRef]
  57. Scott, J.T.; McCarthy, M.J.; Gardner, W.S.; Doyle, R.D. Denitrification, Dissimilatory Nitrate Reduction to Ammonium, and Nitrogen Fixation along a Nitrate Concentration Gradient in a Created Freshwater Wetland. Biogeochemistry 2008, 87, 99–111. [Google Scholar] [CrossRef]
  58. Zhang, Y.; Chen, L.; Dai, T.; Tian, J.; Wen, D. The Influence of Salinity on the Abundance, Transcriptional Activity, and Diversity of AOA and AOB in an Estuarine Sediment: A Microcosm Study. Appl. Microbiol. Biotechnol. 2015, 99, 9825–9833. [Google Scholar] [CrossRef]
  59. Wang, H.; Gilbert, J.A.; Zhu, Y.; Yang, X. Salinity Is a Key Factor Driving the Nitrogen Cycling in the Mangrove Sediment. Sci. Total Environ. 2018, 631–632, 1342–1349. [Google Scholar] [CrossRef] [PubMed]
  60. Li, M.; Gu, J.D. Community Structure and Transcript Responses of Anammox Bacteria, AOA, and AOB in Mangrove Sediment Microcosms Amended with Ammonium and Nitrite. Appl. Microbiol. Biotechnol. 2013, 97, 9859–9874. [Google Scholar] [CrossRef] [PubMed]
  61. Wang, H.; Su, J.; Zheng, T.; Yang, X. Insights into the Role of Plant on Ammonia-Oxidizing Bacteria and Archaea in the Mangrove Ecosystem. J. Soils Sediments 2015, 15, 1212–1223. [Google Scholar] [CrossRef]
  62. Guo, H.; Ma, L.; Liang, Y.; Hou, Z.; Min, W. Response of Ammonia-Oxidizing Bacteria and Archaea to Long-Term Saline Water Irrigation in Alluvial Grey Desert Soils. Sci. Rep. 2020, 10, 489. [Google Scholar] [CrossRef] [PubMed]
  63. Kaushik, A.; Sethi, V. Salinity Effects on Nitrifying and Free Diazotrophic Bacterial Populations in the Rhizosphere of Rice. Bull. Natl. Inst. Ecol. 2005, 15, 139–144. [Google Scholar]
  64. Magalhães, C.M.; Joye, S.B.; Moreira, R.M.; Wiebe, W.J.; Bordalo, A.A. Effect of Salinity and Inorganic Nitrogen Concentrations on Nitrification and Denitrification Rates in Intertidal Sediments and Rocky Biofilms of the Douro River Estuary, Portugal. Water Res. 2005, 39, 1783–1794. [Google Scholar] [CrossRef] [PubMed]
  65. Liu, B.; Zhao, W.; Wen, Z.; Yang, Y.; Chang, X.; Yang, Q.; Meng, Y.Y.; Liu, C. Mechanisms and Feedbacks for Evapotranspiration-Induced Salt Accumulation and Precipitation in an Arid Wetland of China. J. Hydrol. 2019, 568, 403–415. [Google Scholar] [CrossRef]
  66. Meng, Y.; He, Z.; Liu, B.; Chen, L.; Lin, P.; Luo, W. Soil Salinity and Moisture Control the Processes of Soil Nitrification and Denitrification in a Riparian Wetlands in an Extremely Arid Regions in Northwestern China. Water 2020, 12, 2815. [Google Scholar] [CrossRef]
  67. Fagodiya, R.K.; Kumar, A.; Kumari, S.; Medhi, K.; Shabnam, A.A. Role of Nitrogen and Its Agricultural Management in Changing Environment. In Contaminants in Agriculture; Springer: Berlin/Heidelberg, Germany, 2020; pp. 247–270. ISBN 9783030415525. [Google Scholar]
  68. Braker, G.; Conrad, R. Diversity, Structure, and Size of N2O-Producing Microbial Communities in Soils—What Matters for Their Functioning? Adv. Appl. Microbiol. 2011, 75, 33–70. [Google Scholar] [PubMed]
  69. Wang, X.; Wang, S.; Shi, G.; Wang, W.; Zhu, G. Factors Driving the Distribution and Role of AOA and AOB in Phragmites Communis Rhizosphere in Riparian Zone. J. Basic Microbiol. 2019, 59, 425–436. [Google Scholar] [CrossRef] [PubMed]
  70. Zhang, L.; Song, L.; Zhang, L.; Shao, H.; Chen, X.; Yan, K. Seasonal Dynamics in Nitrous Oxide Emissions under Different Types of Vegetation in Saline-Alkaline Soils of the Yellow River Delta, China and Implications for Eco-Restoring Coastal Wetland. Ecol. Eng. 2013, 61, 82–89. [Google Scholar] [CrossRef]
  71. Shao, X.; Zhao, L.; Sheng, X.; Wu, M. Effects of Influent Salinity on Water Purification and Greenhouse Gas Emissions in Lab-Scale Constructed Wetlands. Environ. Sci. Pollut. Res. 2020, 27, 21487–21496. [Google Scholar] [CrossRef]
  72. Fiedler, D.J.; Clay, D.E.; Joshi, D.R.; Engel, A.; Marzano, S.Y.; Jakubowski, D.; Bhattarai, D.; Reese, C.L.; Bruggeman, S.A.; Clay, S.A. CO2 and N2O Emissions and Microbial Community Structure from Fields That Include Salt-Affected Soils. J. Environ. Qual. 2021, 50, 567–579. [Google Scholar] [CrossRef]
  73. Dalal, R.C.; Wang, W.; Robertson, G.P.; Parton, W.J. Nitrous Oxide Emission from Australian Agricultural Lands and Mitigation Options: A Review. Aust. J. Soil Res. 2003, 41, 165–195. [Google Scholar] [CrossRef]
  74. Wang, D.; Chen, Z.; Sun, W.; Hu, B.; Xu, S. Methane and Nitrous Oxide Concentration and Emission Flux of Yangtze Delta Plain River Net. Sci. China Ser. B Chem. 2009, 52, 652–661. [Google Scholar] [CrossRef]
  75. Costa, K.C.; Leigh, J.A. Metabolic Versatility in Methanogens. Curr. Opin. Biotechnol. 2014, 29, 70–75. [Google Scholar] [CrossRef]
  76. Ollivier, B.; Caumette, P.; Garcia, J.L.; Mah, R.A. Anaerobic Bacteria from Hypersaline Environments. Microbiol. Rev. 1994, 58, 27–38. [Google Scholar] [CrossRef]
  77. Scholten, J.C.M.; Joye, S.B.; Hollibaugh, J.T.; Murrell, J.C. Molecular Analysis of the Sulfate Reducing and Archaeal Community in a Meromictic Soda Lake (Mono Lake, California) by Targeting 16S RRNA, McrA, ApsA, and DsrAB Genes. Microb. Ecol. 2005, 50, 29–39. [Google Scholar] [CrossRef]
  78. Bebout, B.M.; Hoehler, T.M.; Thamdrup, B.; Albert, D.; Carpenter, S.P.; Hogan, M.; Turk, K.; Des Marais, D.J. Methane Production by Microbial Mats under Low Sulphate Concentrations. Geobiology 2004, 2, 87–96. [Google Scholar] [CrossRef]
  79. Smith, J.M.; Green, S.J.; Kelley, C.A.; Prufert-Bebout, L.; Bebout, B.M. Shifts in Methanogen Community Structure and Function Associated with Long-Term Manipulation of Sulfate and Salinity in a Hypersaline Microbial Mat. Environ. Microbiol. 2008, 10, 386–394. [Google Scholar] [CrossRef] [PubMed]
  80. Heyer, J.; Berger, U.; Hardt, M.; Dunfield, P.F. Methylohalobius Crimeensis Gen. Nov., Sp. Nov., a Moderately Halophilic, Methanotrophic Bacterium Isolated from Hypersaline Lakes of Crimea. Int. J. Syst. Evol. Microbiol. 2005, 55, 1817–1826. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  81. Nguyen, B.T.; Trinh, N.N.; Bach, Q.V. Methane Emissions and Associated Microbial Activities from Paddy Salt-Affected Soil as Influenced by Biochar and Cow Manure Addition. Appl. Soil Ecol. 2020, 152, 103531. [Google Scholar] [CrossRef]
  82. Xiao, K.; Guo, C.; Maspolim, Y.; Zhou, Y.; Ng, W.J. The Role of Methanogens in Acetic Acid Production under Different Salinity Conditions. Chemosphere 2016, 161, 53–60. [Google Scholar] [CrossRef]
  83. Theint, E.E.; Suzuki, S.; Ono, E.; Bellingrath-Kimura, S.D. Influence of Different Rates of Gypsum Application on Methane Emission from Saline Soil Related with Rice Growth and Rhizosphere Exudation. Catena 2015, 133, 467–473. [Google Scholar] [CrossRef]
  84. Weston, N.B.; Vile, M.A.; Neubauer, S.C.; Velinsky, D.J. Accelerated Microbial Organic Matter Mineralization Following Salt-Water Intrusion into Tidal Freshwater Marsh Soils. Biogeochemistry 2011, 102, 135–151. [Google Scholar] [CrossRef]
  85. Li, Y.; Xu, J.; Liu, B.; Wang, H.; Qi, Z.; Wei, Q.; Liao, L.; Liu, S. Enhanced N2O Production Induced by Soil Salinity at a Specific Range. Int. J. Environ. Res. Public Health 2020, 17, 5169. [Google Scholar] [CrossRef]
  86. THAPA, R.; CHATTERJEE, A.; WICK, A.; BUTCHER, K. Carbon Dioxide and Nitrous Oxide Emissions from Naturally Occurring Sulfate-Based Saline Soils at Different Moisture Contents. Pedosphere 2017, 27, 868–876. [Google Scholar] [CrossRef]
  87. Wei, Q.; Xu, J.; Liao, L.; Li, Y.; Wang, H.; Rahim, S.F. Water Salinity Should Be Reduced for Irrigation to Minimize Its Risk of Increased Soil N2O Emissions. Int. J. Environ. Res. Public Health 2018, 15, 2114. [Google Scholar] [CrossRef]
  88. Zhang, H.; Tang, J.; Liang, S.; Li, Z.; Yang, P.; Wang, J.; Wang, S. The Emissions of Carbon Dioxide, Methane, and Nitrous Oxide during Winter without Cultivation in Local Saline-Alkali Rice and Maize Fields in Northeast China. Sustainability 2017, 9, 1916. [Google Scholar] [CrossRef]
  89. Poffenbarger, H.J.; Needelman, B.A.; Megonigal, J.P. Salinity Influence on Methane Emissions from Tidal Marshes. Wetlands 2011, 31, 831–842. [Google Scholar] [CrossRef]
  90. She, R.; Yu, Y.; Ge, C.; Yao, H. Soil Texture Alters the Impact of Salinity on Carbon Mineralization. Agronomy 2021, 11, 128. [Google Scholar] [CrossRef]
  91. Zhang, L.; Song, L.; Wang, B.; Shao, H.; Zhang, L.; Qin, X. Co-Effects of Salinity and Moisture on CO2 and N2O Emissions of Laboratory-Incubated Salt-Affected Soils from Different Vegetation Types. Geoderma 2018, 332, 109–120. [Google Scholar] [CrossRef]
  92. Pattnaik, P.; Mishra, S.R.; Bharati, K.; Mohanty, S.R.; Sethunathan, N.; Adhya, T.K. Influence of Salinity on Methanogenesis and Associated Microflora in Tropical Rice Soils. Microbiol. Res. 2000, 155, 215–220. [Google Scholar] [CrossRef]
  93. Low, A.P.; Stark, J.M.; Dudley, L.M. Effects of Soil Osmotic Potential on Nitrification, Ammonification, N-Assimilation, and Nitrous Oxide Production. Soil Sci. 1997, 162, 16–27. [Google Scholar] [CrossRef]
  94. Jäntti, H.; Aalto, S.L.; Paerl, H.W. Effects of Ferrous Iron and Hydrogen Sulfide on Nitrate Reduction in the Sediments of an Estuary Experiencing Hypoxia. Estuaries and Coasts 2021, 44, 1–12. [Google Scholar] [CrossRef]
  95. Sørensen, J.; Tiedje, J.M.; Firestone, R.B. Inhibition by Sulfide of Nitric and Nitrous Oxide Reduction by Denitrifying Pseudomonas Fluorescens. Appl. Environ. Microbiol. 1980, 39, 105–108. [Google Scholar] [CrossRef] [PubMed]
  96. Han, Z.; Dong, J.; Shen, Z.; Mou, R.; Zhou, Y.; Chen, X.; Fu, X.; Yang, C. Nitrogen Removal of Anaerobically Digested Swine Wastewater by Pilot-Scale Tidal Flow Constructed Wetland Based on in-Situ Biological Regeneration of Zeolite. Chemosphere 2019, 217, 364–373. [Google Scholar] [CrossRef] [PubMed]
  97. Jia, W.; Sun, X.; Gao, Y.; Yang, Y.; Yang, L. Fe-Modified Biochar Enhances Microbial Nitrogen Removal Capability of Constructed Wetland. Sci. Total Environ. 2020, 740, 139534. [Google Scholar] [CrossRef]
  98. Laura, R.D. Salinity and Nitrogen Mineralization in Soil. Soil Biol. Biochem. 1977, 9, 333–336. [Google Scholar] [CrossRef]
  99. Weston, N.B.; Giblin, A.E.; Banta, G.T.; Hopkinson, C.S.; Tucker, J. The Effects of Varying Salinity on Ammonium Exchange in Estuarine Sediments of the Parker River, Massachusetts. Estuaries and Coasts 2010, 33, 985–1003. [Google Scholar] [CrossRef]
  100. Xu, S.; Fu, X.; Ma, S.; Bai, Z.; Xiao, R.; Li, Y.; Zhuang, G. Mitigating Nitrous Oxide Emissions from Tea Field Soil Using Bioaugmentation with a Trichoderma Viride Biofertilizer. Sci. World J. 2014, 2014, 793752. [Google Scholar] [CrossRef] [Green Version]
  101. Ilgrande, C.; Leroy, B.; Wattiez, R.; Vlaeminck, S.E.; Boon, N.; Clauwaert, P. Metabolic and Proteomic Responses to Salinity in Synthetic Nitrifying Communities of Nitrosomonas spp. And Nitrobacter spp. Front. Microbiol. 2018, 9, 2914. [Google Scholar] [CrossRef]
  102. Babbin, A.R.; Tamasi, T.; Dumit, D.; Weber, L.; Rodríguez, M.V.I.; Schwartz, S.L.; Armenteros, M.; Wankel, S.D.; Apprill, A. Discovery and Quantification of Anaerobic Nitrogen Metabolisms among Oxygenated Tropical Cuban Stony Corals. ISME J. 2021, 15, 1222–1235. [Google Scholar] [CrossRef]
  103. Zhao, Y.; Xia, Y.; Li, B.; Yan, X. Influence of Environmental Factors on Net N2 and N2O Production in Sediment of Freshwater Rivers. Environ. Sci. Pollut. Res. 2014, 21, 9973–9982. [Google Scholar] [CrossRef] [PubMed]
  104. Malyan, S.K.; Singh, O.; Kumar, A.; Anand, G.; Singh, R.; Singh, S.; Yu, Z.; Kumar, J.; Fagodiya, R.K.; Kumar, A. Greenhouse Gases Trade-Off from Ponds: An Overview of Emission Process and Their Driving Factors. Water 2022, 14, 970. [Google Scholar] [CrossRef]
  105. Malyan, S.K.; Kumar, S.S.; Singh, A.; Kumar, O.; Gupta, D.K.; Yadav, A.N.; Fagodiya, R.K.; Khan, S.A.; Kumar, A. Understanding Methanogens, Methanotrophs, and Methane Emission in Rice Ecosystem. In Microbiomes and the Global Climate Change; Springer: Singapore, 2021; pp. 205–224. ISBN 9789813345089. [Google Scholar]
  106. Hussain, S.; Peng, S.; Fahad, S.; Khaliq, A.; Huang, J.; Cui, K.; Nie, L. Rice Management Interventions to Mitigate Greenhouse Gas Emissions: A Review. Environ. Sci. Pollut. Res. 2015, 22, 3342–3360. [Google Scholar] [CrossRef]
  107. Vo, T.B.T.; Wassmann, R.; Tirol-Padre, A.; Cao, V.P.; MacDonald, B.; Espaldon, M.V.O.; Sander, B.O. Methane Emission from Rice Cultivation in Different Agro-Ecological Zones of the Mekong River Delta: Seasonal Patterns and Emission Factors for Baseline Water Management. Soil Sci. Plant Nutr. 2018, 64, 47–58. [Google Scholar] [CrossRef]
  108. Sun, M.; Zhang, H.; Dong, J.; Gao, F.; Li, X.; Zhang, R. A Comparison of CH4 Emissions from Coastal and Inland Rice Paddy Soils in China. Catena 2018, 170, 365–373. [Google Scholar] [CrossRef]
  109. Datta, A.; Yeluripati, J.B.; Nayak, D.R.; Mahata, K.R.; Santra, S.C.; Adhya, T.K. Seasonal Variation of Methane Flux from Coastal Saline Rice Field with the Application of Different Organic Manures. Atmos. Environ. 2013, 66, 114–122. [Google Scholar] [CrossRef]
  110. Kumar, S.S.; Malyan, S.K.; Basu, S.; Bishnoi, N.R. Syntrophic Association and Performance of Clostridium, Desulfovibrio, Aeromonas and Tetrathiobacter as Anodic Biocatalysts for Bioelectricity Generation in Dual Chamber Microbial Fuel Cell. Environ. Sci. Pollut. Res. 2017, 24, 16019–16030. [Google Scholar] [CrossRef]
  111. Setia, R.; Marschner, P.; Baldock, J.; Chittleborough, D.; Verma, V. Relationships between Carbon Dioxide Emission and Soil Properties in Salt-Affected Landscapes. Soil Biol. Biochem. 2011, 43, 667–674. [Google Scholar] [CrossRef]
  112. Enzmann, F.; Mayer, F.; Rother, M.; Holtmann, D. Methanogens: Biochemical Background and Biotechnological Applications. AMB Express 2018, 8, 1. [Google Scholar] [CrossRef]
  113. Das, S.; Ganguly, D.; De, T.K. Microbial Methane Production-Oxidation Profile in the Soil of Mangrove and Paddy Fields of West Bengal, India. Geomicrobiol. J. 2020, 38, 220–230. [Google Scholar] [CrossRef]
  114. Saifullah; Dahlawi, S.; Naeem, A.; Rengel, Z.; Naidu, R. Biochar Application for the Remediation of Salt-Affected Soils: Challenges and Opportunities. Sci. Total Environ. 2018, 625, 320–335. [Google Scholar] [CrossRef]
  115. Shi, Y.; Liu, X.; Zhang, Q. Effects of Combined Biochar and Organic Fertilizer on Nitrous Oxide Fluxes and the Related Nitrifier and Denitrifier Communities in a Saline-Alkali Soil. Sci. Total Environ. 2019, 686, 199–211. [Google Scholar] [CrossRef]
  116. Yu, Y.; Li, X.; Zhao, C.; Zheng, N.; Jia, H.; Yao, H. Soil Salinity Changes the Temperature Sensitivity of Soil Carbon Dioxide and Nitrous Oxide Emissions. Catena 2020, 195, 104912. [Google Scholar] [CrossRef]
  117. Toor, M.; Kumar, S.S.; Malyan, S.K.; Bishnoi, N.R.; Mathimani, T.; Rajendran, K.; Pugazhendhi, A. An Overview on Bioethanol Production from Lignocellulosic Feedstocks. Chemosphere 2020, 242, 125080. [Google Scholar] [CrossRef]
  118. Sun, L.; Ma, Y.; Liu, Y.; Li, J.; Deng, J.; Rao, X.; Zhang, Y. The Combined Effects of Nitrogen Fertilizer, Humic Acid, and Gypsum on Yield-Scaled Greenhouse Gas Emissions from a Coastal Saline Rice Field. Environ. Sci. Pollut. Res. 2019, 26, 19502–19511. [Google Scholar] [CrossRef]
  119. Ali, M.K.; Ahmad, W.; Malhi, S.S.; Atta, B.M.; Ghafoor, A.; Zia, M.H. Potential of Carbon Dioxide Biosequestration of Saline-Sodic Soils during Amelioration under Rice-Wheat Land Use. Commun. Soil Sci. Plant Anal. 2013, 44, 2625–2635. [Google Scholar] [CrossRef]
  120. Kim, Y.J.; Choo, B.K.; Cho, J.Y. Effect of Gypsum and Rice Straw Compost Application on Improvements of Soil Quality during Desalination of Reclaimed Coastal Tideland Soils: Ten Years of Long-Term Experiments. Catena 2017, 156, 131–138. [Google Scholar] [CrossRef]
  121. Ding, Z.; Kheir, A.M.S.; Ali, O.A.M.; Hafez, E.M.; ElShamey, E.A.; Zhou, Z.; Wang, B.; Lin, X.; Ge, Y.; Fahmy, A.E.; et al. A Vermicompost and Deep Tillage System to Improve Saline-Sodic Soil Quality and Wheat Productivity. J. Environ. Manag. 2021, 277. [Google Scholar] [CrossRef] [PubMed]
  122. Abou Hussien, E.; Ahmed, B.; Elbaalawy, A. Efficiency of Azolla and Biochar Application on Rice (Oryza Sativa L.) Productivity in Salt-Affected Soil. Egypt. J. Soil Sci. 2020, 60, 277–288. [Google Scholar] [CrossRef]
  123. Li, H.; Zhao, Q.; Huang, H. Current States and Challenges of Salt-Affected Soil Remediation by Cyanobacteria. Sci. Total Environ. 2019, 669, 258–272. [Google Scholar] [CrossRef] [PubMed]
  124. Singh, K.; Singh, B.; Tuli, R. Sodic Soil Reclamation Potential of Jatropha Curcas: A Long-Term Study. Ecol. Eng. 2013, 58, 434–440. [Google Scholar] [CrossRef]
  125. Sarwar, G.; Malik, M.A.; Tahir, M.A.; Aftab, M.; Manzoor, M.Z.; Zafar, A. Comparative Efficiency of Compost, Farmyard Manure and Sesbania Green Manure to Produce Rice-Wheat Crops under Salt Stressed Environmental Conditions. J. Pure Appl. Agric. 2020, 5, 33–42. [Google Scholar]
  126. Li, Y.; Xu, J.; Liu, X.; Qi, Z.; Wang, H.; Li, Y.; Liao, L. Nitrification Inhibitor DMPP Offsets the Increase in N2O Emission Induced by Soil Salinity. Biol. Fertil. Soils 2020, 56, 1211–1217. [Google Scholar] [CrossRef]
  127. Denier van der Gon, H.A.C.; Neue, H.U. Impact of Gypsum Application on the Methane Emission from a Wetland Rice Field. Global Biogeochem. Cycles 1994, 8, 127–134. [Google Scholar] [CrossRef]
  128. Epule, E.T.; Peng, C.; Mafany, N.M. Methane Emissions from Paddy Rice Fields: Strategies towards Achieving A Win-Win Sustainability Scenario between Rice Production and Methane Emission Reduction. J. Sustain. Dev. 2011, 4. [Google Scholar] [CrossRef]
  129. Gauci, V.; Matthews, E.; Dise, N.; Walter, B.; Koch, D.; Granberg, G.; Vile, M. Sulfur Pollution Suppression of the Wetland Methane Source in the 20th and 21st Centuries. Proc. Natl. Acad. Sci. USA 2004, 101, 12583–12587. [Google Scholar] [CrossRef] [PubMed]
  130. Denier van der Gon, H.A.; van Bodegom, P.M.; Wassmann, R.; Lantin, R.S.; Metra-Corton, T.M. Sulfate-Containing Amendments to Reduce Methane Emissions from Rice Fields: Mechanisms, Effectiveness and Costs. Mitig. Adapt. Strateg. Glob. Chang. 2001, 6, 71–89. [Google Scholar] [CrossRef]
  131. Park, J.-H.; Sonn, Y.-K.; Kong, M.-S.; Zhang, Y.-S.; Park, S.-J.; Won, J.-G.; Lee, S.-H.; Seo, D.-H.; Park, S.-D.; Kim, J.-E. Effect of By-Product Gypsum Fertilizer on Methane Gas Emissions and Rice Productivity in Paddy Field. Korean J. Soil Sci. Fertil. 2016, 49, 30–35. [Google Scholar] [CrossRef]
  132. Ali, M.; Farouque, M.; Haque, M.; Ul Kabir, A. Influence of Soil Amendments on Mitigating Methane Emissions and Sustaining Rice Productivity in Paddy Soil Ecosystems of Bangladesh. J. Environ. Sci. Nat. Resour. 2012, 5, 179–185. [Google Scholar] [CrossRef] [Green Version]
  133. Sun, L.; Deng, J.; Fan, C.; Li, J.; Liu, Y. Combined Effects of Nitrogen Fertilizer and Biochar on Greenhouse Gas Emissions and Net Ecosystem Economic Budget from a Coastal Saline Rice Field in Southeastern China. Environ. Sci. Pollut. Res. 2020, 27, 17013–17022. [Google Scholar] [CrossRef]
  134. Chen, Z.; Huang, G.; Li, Y.; Zhang, X.; Xiong, Y.; Huang, Q.; Jin, S. Effects of the Lignite Bioorganic Fertilizer on Greenhouse Gas Emissions and Pathways of Nitrogen and Carbon Cycling in Saline-Sodic Farmlands at Northwest China. J. Clean. Prod. 2022, 334, 130080. [Google Scholar] [CrossRef]
  135. Zheng, N.; Yu, Y.; Li, Y.; Ge, C.; Chapman, S.J.; Yao, H. Can Aged Biochar Offset Soil Greenhouse Gas Emissions from Crop Residue Amendments in Saline and Non-Saline Soils under Laboratory Conditions? Sci. Total Environ. 2022, 806, 151256. [Google Scholar] [CrossRef]
  136. Malyan, S.K.; Kumar, S.S.; Fagodiya, R.K.; Ghosh, P.; Kumar, A.; Singh, R.; Singh, L. Biochar for Environmental Sustainability in the Energy-Water-Agroecosystem Nexus. Renew. Sustain. Energy Rev. 2021, 149, 111379. [Google Scholar] [CrossRef]
  137. Yu, Y.; Zhao, C.; Zheng, N.; Jia, H.; Yao, H. Interactive Effects of Soil Texture and Salinity on Nitrous Oxide Emissions Following Crop Residue Amendment. Geoderma 2019, 337, 1146–1154. [Google Scholar] [CrossRef]
  138. Zhu, H.; Yang, J.; Yao, R.; Wang, X.; Xie, W.; Zhu, W.; Liu, X.; Cao, Y.; Tao, J. Interactive Effects of Soil Amendments (Biochar and Gypsum) and Salinity on Ammonia Volatilization in Coastal Saline Soil. Catena 2020, 190. [Google Scholar] [CrossRef]
  139. Bhattacharya, S.S.; Kim, K.H.; Das, S.; Uchimiya, M.; Jeon, B.H.; Kwon, E.; Szulejko, J.E. A Review on the Role of Organic Inputs in Maintaining the Soil Carbon Pool of the Terrestrial Ecosystem. J. Environ. Manag. 2016, 167, 214–227. [Google Scholar] [CrossRef] [PubMed]
  140. Bharali, A.; Baruah, K.K.; Bhattacharya, S.S.; Kim, K.H. The Use of Azolla Caroliniana Compost as Organic Input to Irrigated and Rainfed Rice Ecosystems: Comparison of Its Effects in Relation to CH4 Emission Pattern, Soil Carbon Storage, and Grain C Interactions. J. Clean. Prod. 2021, 313, 127931. [Google Scholar] [CrossRef]
  141. Nan, Q.; Wang, C.; Wang, H.; Yi, Q.; Wu, W. Mitigating Methane Emission via Annual Biochar Amendment Pyrolyzed with Rice Straw from the Same Paddy Field. Sci. Total Environ. 2020, 746, 141351. [Google Scholar] [CrossRef] [PubMed]
  142. Singh, J.S.; Pandey, V.C.; Singh, D.P.; Singh, R.P. Influence of Pyrite and Farmyard Manure on Population Dynamics of Soil Methanotroph and Rice Yield in Saline Rain-Fed Paddy Field. Agric. Ecosyst. Environ. 2010, 139, 74–79. [Google Scholar] [CrossRef]
  143. Wang, M.; Wang, C.; Lan, X.; Abid, A.A.; Xu, X.; Singla, A.; Sardans, J.; Llusià, J.; Peñuelas, J.; Wang, W. Coupled Steel Slag and Biochar Amendment Correlated with Higher Methanotrophic Abundance and Lower CH4 Emission in Subtropical Paddies. Environ. Geochem. Health 2020, 42, 483–497. [Google Scholar] [CrossRef]
  144. Supparattanapan, S.; Saenjan, P.; Quantin, C.; Maeght, J.L.; Grünberger, O. Salinity and Organic Amendment Effects on Methane Emission from a Rain-Fed Saline Paddy Field. Soil Sci. Plant Nutr. 2009, 55, 142–149. [Google Scholar] [CrossRef]
Figure 1. Global area of salt-affected soils and their distribution in the different regions of the world (Source: FAO and ITPS [43]).
Figure 1. Global area of salt-affected soils and their distribution in the different regions of the world (Source: FAO and ITPS [43]).
Sustainability 14 11876 g001
Figure 5. Mechanism of carbon dioxide production in saline soils.
Figure 5. Mechanism of carbon dioxide production in saline soils.
Sustainability 14 11876 g005
Table 1. Types/classes of salt-affected soils and their chemical characteristics.
Table 1. Types/classes of salt-affected soils and their chemical characteristics.
Salinity ClassECe
(dS m−1)
ESP(pHs)(SARe)Type of Dominant SaltsProblems Associated
Saline soils>4<15<8.5<13High levels of soluble salts of chlorides (Cl) and sulfate (SO42−) of sodium (Na+), calcium (Ca2+), and magnesium (Mg2+)Hinder water absorption by plants due to high osmotic effects. Possible toxicity and antagonism of dominant ions at higher electrical conductivity
Alkali/sodic Soils<4>15>8.5>13High concentration of carbonate (CO32−) and bicarbonate (HCO3) salts of sodium (Na+) in soil solution, and Na+ on exchange sitesSodium, Carbonate, and bicarbonate toxicity to plants. Dispersion of soil structure due to high sodium content. Slaking, swelling, and hard setting of soil surface. Seasonal waterlogging
Saline-alkali/sodic soils>4>15Variable>13The combined effect of excess salts and high exchangeable sodium percentageHinder water and nutrients uptake due to high osmotic effects. Sodium, carbonate, and bicarbonate toxicity to plants. Dispersion of soil structure due to high sodium content. Slaking, swelling, and hard setting of soil surface
ECe = electrical conductivity of saturated paste extract; pHs = pH of saturated paste; ESP = exchangeable sodium percentage; SARe = sodium adsorption ratio in saturated paste extract.
Table 3. Different amendments/materials used for the management of salt-affected soils and mitigation of GHG emissions.
Table 3. Different amendments/materials used for the management of salt-affected soils and mitigation of GHG emissions.
S. No. Amendment Details References
01Gypsum/phosphogypsum [83,118,119]
03Humic acid [118]
04Rice straw compost [120]
05Cow manure [81]
06Deep tillage [121]
07Vermicompost [121]
08Azolla application [122]
09Cyanobacteria [123]
10Jatropha curcas[124]
11Sesbania green manure [125]
12Nitrification inhibitors (3,4-Dimethylpyrazole phosphate)[126]
Table 4. Impact of different amendments practices on GHG emissions from salt-affected soils.
Table 4. Impact of different amendments practices on GHG emissions from salt-affected soils.
ReferencesExperiment TypeTreatment’s DetailObservation (GHG Emissions)Key Findings and Reasoning
Application of gypsum and phosphogypsum
Khatun et al. [28]Pot experiment
Initial soil pH = 7.8, EC = 5.6 dS m−1, OC = 1.48%
25 nM salinity; 25 nM + phosphogypsum (P); 50 nM; 50 nM + P; 75 nM; 75 nM + PBiochar amendment to saline soil reduced CH4 emission by 16.4% (25 mM) to 19.6% (at 75 mM)Phospho-gypsum and biochar mitigate CH4 emissions due to improved soil redox potential (Eh), increased SO4 and decreased soil EC.
Sun et al. [118]Field experiment growing rice conducted in Jiangsu Province, ChinaN1 (300 kg N ha−1); N1 + humic acid; N1 + gypsum; N1 + humic acid + gypsumCH4 emissions increased with Humic acid (6.2%), gypsum (19.4%), decreased with gypsum + humic acid (27.3%). Humic acid and gypsum application increase N2O emission Humic acid and gypsum application with N300 kg N ha−1 is the better management for coastal saline soils of China to mitigate CH4 emission.
Park et al. [131]Field experiment with rice.No by-product gypsum fertilizer (BGF); BGF (2 Mg ha−1); BGF (4 Mg ha−1); BGF (8 Mg ha−1)CH4 flux decreased with increasing level of BGF, and BGF (8 Mg ha−1) reduced it by 60.6% compared to control.BGF application could be a better management practice for CH4 mitigation from paddy soils.
Ali et al. [132]Field experiment with rice in upland soil.Urea (250 kg ha−1); Urea + Phosphogypsum (90 kg ha−1); Urea + silicate slag (150 kg ha−1)Silicate slag and phosphogypsum reduced CH4 emission by 18.0–23.5% and 14.7–18.6%, respectively. Silicate slag and phosphogypsum decreased CH4 due to high free iron oxide and SO42− content which acted as electron acceptors
Denier van der Gon and Neue, [127]Field experiment with rice.Urea (165 kg N ha−1); Urea + gypsum (6.60 t ha−1)The CH4 emissions from gypsum amended plots were reduced by 55–70% compared to non-amended plots.Inhibition of methanogenesis by sulfate-reducing bacteria caused a reduction in CH4 emission.
Application of organic amendments (biochar, organic matter etc)
Sun et al. [133]Field experiment with riceN1 (300 kg N ha−1); N1 + 20 t biochar ha−1; N1 + 40 t biochar ha−1Biochar amendment increased N2O emissions by 13.7–38.1% and had no significant effects on CH4 emissionsThus, long-term observations are needed to evaluate the environmental impacts of biochar and N fertilizers
Maucieri et al. [24]30 days incubation experimentControl; BiocharBiochar amendment to saline soil decrease CH4 uptake (8.8%), CO2 (11.9%), and N2O (9.8%) emissionsBiochar amendment to soils mitigates GHG emissions where CO2 and N2O are driven by soil rewetting events.
Datta et al. [109]Rice experiment in irrigated saline soils of Gadakujang (a fishing hamlet) of coastal Odisha, IndiaPrilled urea (40 kg N ha−1); Sesbania green manure (5 Mg ha−1) + prilled urea (20 kg N ha−1); Ipomoea lacunose (5 Mg ha−1) + prilled urea (28 kg N ha−1)Sesbania and Ipomoea lacunose green manure reduced CH4 emission by 23.2 and 29.9%.Locally available Ipomoea lacunose green manure can use CH4 mitigation and yield enhancement from the coastal saline rice ecosystems
Denier van der Gon and Neue, [127]Field experiment with riceGM (S. Rostrata: 20 t ha−1) + urea (30 kg urea ha−1); GM + urea + gypsum (6.60 t ha−1)Green manure addition enhances CH4 emissions by 10 times than that of urea application alone, further gypsum addition reduced CH4 emission by about 71.1%Database for CH4 emissions mitigation from rice grown on high-sulfate containing soils
Chen et al. [134]Field experiment was conducted in saline-sodic soils in the upper Yellow River basin, Northwest ChinaOrganic fertilizer (CK), sheep manure (FYM), lignite bioorganic fertilizer (LBF1) (1.5 t ha−1) LBF2 (3 t ha−1), LBF3 (4.5 t ha−1), and LBF4 (7.5 t ha−1)LBF treatments decreased CH4 and CO2, and increasing N2O emissions beyond 3 t ha−1 application rate. FYM acted as a CH4 source, and LBF2 and LBF3 treatments acted as CH4 sinks.The application of lignite bioorganic fertilizer at 3.0–4.5 t ha−1 is appropriate for GHG mitigation in saline-sodic farmlands.
Zheng et al. [135]Microcosm experiments of 80 days incubationInteraction of salinity (0 and 1.2% salt) with biochar 5–10 times higher N2O emissions occurred from saline soils than that from non-saline soils.
Aged biochar decreased N2O emissions and increased CO2 emissions in saline soils.
Aged biochar could be a better option for mitigation of N2O emissions from saline soils.
Other amendments/interventions
Li et al. [126]Field experiment with rice cropNonsaline (NS) soi; NS soil + DMPP (0.8% w/w of N); low saline (LS) soil; LS soil + DMPP; high saline (HS) soil; HS soil + DMPPThe nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) reduced cumulative N2O emissions by 61% in non-saline soil and by 75% in low saline soilDMPP offsets low salinity-induced high N2O emissions by inhibiting ammonia oxidation.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Fagodiya, R.K.; Malyan, S.K.; Singh, D.; Kumar, A.; Yadav, R.K.; Sharma, P.C.; Pathak, H. Greenhouse Gas Emissions from Salt-Affected Soils: Mechanistic Understanding of Interplay Factors and Reclamation Approaches. Sustainability 2022, 14, 11876.

AMA Style

Fagodiya RK, Malyan SK, Singh D, Kumar A, Yadav RK, Sharma PC, Pathak H. Greenhouse Gas Emissions from Salt-Affected Soils: Mechanistic Understanding of Interplay Factors and Reclamation Approaches. Sustainability. 2022; 14(19):11876.

Chicago/Turabian Style

Fagodiya, Ram K., Sandeep K. Malyan, Devendra Singh, Amit Kumar, Rajender K. Yadav, Parbodh C. Sharma, and Himanshu Pathak. 2022. "Greenhouse Gas Emissions from Salt-Affected Soils: Mechanistic Understanding of Interplay Factors and Reclamation Approaches" Sustainability 14, no. 19: 11876.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop